MURPHY, Circuit Judge.
This ease raises questions about the extent to which an 1894 act of Congress affected the reservation of the Yankton Sioux Tribe in South Dakota. That statute ratified and incorporated an 1892 agreement between the tribe and the United States. The tribe brought this declaratory judgment action to enforce its claimed right to approve and regulate a landfill site over which the state claims jurisdiction on the basis that the 1894 statute disestablished or diminished the Yankton reservation. After a trial the dis[1442]*1442trict court1 ruled that the site was still part of the Yankton reservation so federal environmental laws applied, but that the tribe did not have regulatory authority over the project, which it declined to enjoin. The state appealed from the judgment, and we affirm.
I.
The Southern Missouri Waste Management District (Waste District) is a non-profit corporation which was established by several South Dakota counties to develop a regional solid waste landfill, for which it purchased land within the boundaries of Charles Mix County. The proposed site had been owned by a non-Indian but was within the Yankton Sioux Indian Reservation as defined by the 1858 treaty between the tribe and the United States.
The Waste District filed an application with the South Dakota Department of Environment and Natural Resources for a solid waste permit to construct the landfill on the site. The Yankton tribe was concerned about possible effects of the project, and it intervened and participated in the December 1993 administrative hearing on the permit application.
After the state granted the permit, the tribe2 sued the Waste District in federal court to stop construction until it could review and regulate the project. It sought a declaratory judgment that the boundaries established in the 1858 treaty still define the extent of the reservation. The Waste District joined the state as a third party defendant, and the state argued that the tribe had no jurisdictional authority over the 200,000 noncontiguous acres ceded to the United States in 1894.
The case was tried to the court over five days. The tribe’s expert on Yankton Sioux history, Professor Herbert Hoover, testified that his research revealed no historical reason to believe the boundaries of the reservation had been changed by the 1894 act. Several witnesses testified for each side as to the potential impact of the landfill on tribal activities, the political organization and history of the tribe, and their perception of the reservation’s boundaries. Much of the trial focused on technical issues relating to the construction and integrity of the landfill.
After considering post-trial briefing by the parties which focused on the legal significance of a savings clause in the 1892 agreement, the district court entered a declaratory judgment. It concluded that the 1894 act ratifying the 1892 agreement did not disestablish or diminish the size of the reservation. Yankton Sioux Tribe v. Southern Missouri Waste Management District, 890 F.Supp. 878, 891 (D.S.D.1995). The landfill site was therefore still part of the reservation, and regulations of the Environmental Protection Agency (EPA) applied, including the requirement that a synthetic liner be installed in each of the landfill cells to prevent leakage.3 The court also concluded that the tribe had not shown a right to regulate the landfill site since it had not established either exception to the general rule that Indian tribes cannot regulate the activities of non-Indians, even on a reservation. Montana v. United States, 450 U.S. 544, 564-66, 101 S.Ct. 1245, 1257-59, 67 L.Ed.2d 493 (1981); see also, A-1 Contractors v. Strate, 76 F.3d 930 (8th Cir.1996) (en banc), cert. granted, — U.S. -, 117 S.Ct. 37, 135 L.Ed.2d 1128 (1996) (matters affecting tribal self-government and consensual relations with the tribe are excepted). The court also declined to enjoin the landfill project so long as it complied with the EPA liner requirement.
[1443]*1443On appeal South Dakota argues that the district court erred as a matter of law in concluding that the 1858 tribal boundaries remain in effect despite the 1892 agreement, its ratification in 1894, and the subsequent sale of unallotted land. It contends that the language of the agreement, its ratifying statute, and surrounding circumstances show that Congress intended that the boundaries established by the treaty of 1858 be disestablished or diminished.4 The tribe responds that the intent and interest of Congress was in purchasing land for resale to non-Indian settlers, not in eliminating tribal authority in the area reserved in the treaty of 1858.5
II.
In the 1858 treaty between the Yankton Sioux and the United States the tribe surrendered over 11 million acres, and the United States in turn agreed “[t]o protect the said Yanetons [sic] in the quiet and peaceable possession” of a 430,000 acre reservation in southern South Dakota and a much smaller reservation in southwestern Minnesota.6 11 Stat. 743. The tribe also received $1.6 million to be paid in annuities over 50 years, as well as funds for a mill, schools, houses, and other expenses related to establishing the reservation.
The decades following the signing of the treaty brought significant changes in federal Indian policy as more settlers moved westward, increasing the demand for places to homestead. Solem v. Bartlett, 465 U.S. 463, 466 & n. 6, 104 S.Ct. 1161, 1163-64 & n. 6, 79 L.Ed.2d 443 (1984). Congress was also confronted with how to deal with tribes whose reservations had once been isolated but were located in areas in which states were then being formed.
In 1887 Congress passed the General Allotment Act (Dawes Act). 24 Stat. 388 (1887), codified at 25 U.S.C. § 331 et seq. The Dawes Act permitted the federal government to allot plots of reservation land to individual Indians. Once the members of a tribe had received their individual allotments (“allotted lands”) from the government, the surplus land (“unallotted lands”) could be sold to non-Indian settlers. It was the government’s policy until the early 1900s to sell reservation lands to settlers only after negotiating an agreement with the relevant tribe.7
The Dawes Act was intended both to advance the “civilization” and welfare of Indians and to provide land for settlement. See DeCoteau, 420 U.S. at 432, 95 S.Ct. at 1087. Although it did not mandate the elimination of reservations, it was hoped that under the allotment policy Indians would benefit from individual ownership and responsibility, abandon their communal notions of property and social organization, and learn to farm from their non-Indian neighbors. Hagen v. Utah, 510 U.S. 399, 402-04, 114 S.Ct. 958, 961, 127 L.Ed.2d 252 (1994). Individual membérs of the Yankton tribe eventually received allotments totallinig about 230,000 acres scattered throughout the reservation. Yankton Sioux Tribe v. United States, 224 Ct.Cl. 62, 623 F.2d 159 (1980).
By 1892 there was considerable pressure from settlers for more land in South Dakota, [1444]*1444and a three member commission was appointed to negotiate with the Yankton Sioux about their unallotted lands. The commission was charged with, reaching an agreement that would allow the United States to buy as much of the unallotted land as the tribe would sell. The record shows that some tribal members were interested in selling because of a severe drought and because of concerns for the elderly and infirm, the status of the Pipestone quarry in Minnesota, and compensation owed tribal members for their service in the United States Army. The government hoped that the new policy would help the Yankton Sioux assimilate. The Senate Committee on Indian Affairs reported that “close contact with the frugal, moral, and industrious people who will settle there will stimulate individual effort and make their progress much more rapid than heretofore.” S.Rep. No. 196, 5Sd Cong., 2d Sess. 1 (1894).
The commission eventually succeeded in securing the signatures of a majority of the male members of the tribe in favor of sale of the unallotted lands. Under the agreement, dated December 31, 1892,8 the federal government would pay $600,000 with interest for some 200,000 acres within the boundaries of the reservation that had been established by the treaty of 1858.9 The government intended then to sell plots of this land to settlers.
The agreement of 1892 contained several key provisions. In Article I the tribe agreed to “cede, sell, relinquish, and convey” all its right and title to transferred land, but Article XVIII stated that “Nothing in this agreement shall be construed to abrogate the treaty of April 19th, 1858” and that all provisions of that treaty “shall be in full force and effect, the same as though this agreement had not been made....” Consistent with the Dawes Act, the agreement also stated that lands allotted to tribal members were to be trust lands of the United States for twenty-five years, rather than grants to the Indians in fee simple. Articles IV, IX.
Congress incorporated the agreement into the ratifying statute in 1894 which passed without significant amendment.10 28 Stat. 286, 319. President Cleveland opened the unallotted lands for settlement by proclamation on May 16,1895.
Congressional policy later changed when it became clear in the first decades of the twentieth century that the allotment policy was failing. Solem, 465 U.S. at 468 n. 9, 104 S.Ct. at 1165 n. 9; Mattz v. Arnett, 412 U.S. 481, 496 n. 18, 93 S.Ct. 2245, 2254 n. 18, 37 L.Ed.2d 92 (1973). A significant number of Indians had not become self-sustaining farmers, and many allotments had been sold off when the allottees died. On the Yankton reservation for instance, only 100,000 of over 200,000 acres originally allotted remained in Indian hands by 1914. Perrin v. United States, 232 U.S. 478, 34 S.Ct. 387, 58 L.Ed. 691 (1914). Critics concluded that the policy of integration by means of allotment had resulted in even greater poverty for Indian [1445]*1445people. See Felix Cohen, Handbook of Federal Indian Law 215-17 (1988 ed.)
Congress responded with the Indian Reorganization Act of 1934, 48 Stat. 984 (1934), codified as amended at 25 U.S.C. § 461 et seq., which once again placed primary emphasis on reservations in its Indian land policy. Id. Congress authorized the Secretary of the Interior to exchange lands held by Indians and non-Indians within each reservation in an attempt to consolidate tribal lands. Id. at § 463e. Nevertheless, the lands owned by Yankton Sioux tribal members remain scattered throughout the area of the 1858 reservation., Most of these lands are held in trust by the United States. Although the trust period was only to run twenty-five years, it was extended by executive order in 1920, Exec. Order April 16, 1920, and then apparently indefinitely by the Indian Reorganization Act in 1934. 48 Stat. 984, § 2.
III.
Certain basic principles are part of the legal framework for the issues raised by the parties. Once a reservation is created by Congress through a ratified treaty or agreement, only Congress can reduce or eliminate it, and it must “clearly evince” its intent to do so. Solem, 465 U.S. at 470, 104 S.Ct. at 1166. Opening a reservation to settlement is not inconsistent with the preservation of existing boundaries, Id., and some agreements and treaties preserved reservation boundaries, see, e.g., Id.; Mattz v. Arnett, 412 U.S. 481, 93 S.Ct. 2245, 37 L.Ed.2d 92 (1973); Seymour v. Superintendent, 368 U.S. 351, 82 S.Ct. 424, 7 L.Ed.2d 346 (1962), while others caused them to be diminished. See, e.g., Hagen v. Utah, 510 U.S. 399, 114 S.Ct. 958, 127 L.Ed.2d 252 (1994); Rosebud Sioux Tribe v. Kneip, 430 U.S. 584, 97 S.Ct. 1361, 51 L.Ed.2d 660 (1977); DeCoteau v. District County Court, 420 U.S. 425, 95 S.Ct. 1082, 43 L.Ed.2d 300 (1975). Ambiguity at any point is to be resolved in favor of the Indians, and diminishment should not be found lightly. Hagen, 510 U.S. at 410-11, 114 S.Ct. at 965. Since federal policy towards Indians has changed over time, cases dealing with disestablishment and diminishment issues present difficult questions of statutory intent. Solem, 465 U.S. at 468, 104 S.Ct. at 1164-65; see also, Hagen, 510 U.S. at 425-27, 114 S.Ct. at 973 (Blackmun, J., dissenting)..
Each agreement with Indian tribes is different and must be evaluated in light of all the circumstances. Hagen, 510 U.S. at 410-13, 114 S.Ct. at 965-66. The Supreme Court has devised a “fairly clean analytical structure” for diminishment cases; this requires consideration of the language of the statute and any agreement it incorporated, the historical context surrounding its passage, and how the land in question has been used since. Id. The parties disagree about the significance of some of the sections of the Yankton agreement and the historical evidence.
A.
The most important factor in determining whether Congress intended to disestablish or diminish the Yankton reservation is the 1894 statute, which incorporated the text of the 1892 agreement. Id. at 410-11, 114 S.Ct. at 965. The state believes the language used to describe the conveyance in Articles I and II is particularly relevant, while the tribe focuses on the savings clause in Article XVIII. Each side claims that other sections in the agreement also support its respective position.
South Dakota argues that the language in Articles I and II of the 1892 agreement makes it clear that Congress intended to disestablish or diminish the Yankton reservation. The full text of Article I is:
The Yankton Tribe of-Dakota or Sioux Indians hereby, cede, sell, relinquish, and convey to the United States all their claim, right, title, and interest in and to all the unallotted lands within the limits of the reservation as set apart to said Indians [in the Treaty of 1858].
Article II provided that the tribe was to receive $600,000 for conveyance of the land.11 [1446]*1446The state argues that the Supreme Court has construed similar language as indicating congressional intent to diminish or disestablish reservations. DeCoteau, 420 U.S. at 445, 95 S.Ct. at 1093.
The tribe responds that the cession language in Article I alone is not controlling. It says that the savings clause in Article XVIII must be considered together with Articles I and II and that the negotiation and legislative histories show that the first two articles were not intended to reduce the size of the reservation.
This court reviewed almost identical language to that in Article I in United States v. Grey Bear, 828 F.2d 1286 (8th Cir.1987), vacated in part on other grounds on rehearing en banc, 863 F.2d 572 (8th Cir.1988), cert. denied, 493 U.S. 1047, 110 S.Ct. 846, 107 L.Ed.2d 840 (1990). In that case the Indians had agreed they would “for the consideration hereinafter named, ... hereby cede, surrender, grant, and convey to the United States all their claim, right, title, and interest” in their unallotted lands. Id. at 1290. The court concluded that the reservation had not been diminished because the agreement, “standing alone, does not evince a clear congressional intent to disestablish the Devils Lake Reservation.” Id. In reaching this conclusion, the court followed the Supreme Court’s practice of looking at a number of factors other than cession language to consider disestablishment issues, including surrounding circumstances such as whether there was a lump sum payment or express acknowledgement by the tribe that its reservation would be diminished. Id. at 1290 n. 5.
The state argues that the $600,000 sale price in Article II, in conjunction with the “cede, sell, relinquish, and convey” language in Article I, gives rise to “an almost 'insurmountable presumption” that Congress' intended to diminish the reservation. Solem, 465 U.S. at 470-71, 104 S.Ct. at 1166. The tribe asserts that the history behind Article II suggests that ,the payment provision in this statute did not indicate intent to diminish the reservation.
Article'll passed in the Senate without modification, but the House of Representatives amended the agreement to provide for payment to the tribe only as portions of the unallotted lands were sold to settlers. 53 Cong.Rec. 8268 (1894). Some believed it inappropriate for the government to make large cash payments when there was no guarantee that all land would be sold. Id. The House later withdrew its amendment apparently to avoid any charge of bad faith for changing the agreed terms. See id. at 8268-71. There was no discussion showing any understanding that a sum certain payment would express an intent that the reservation be diminished.
The commission negotiations indicated that both sides had been interested in seeing that unallotted lands were appraised and sold as individual plots to settlers. Tribal members believed they would receive a higher price if the lands were sold in this manner rather than as a whole to the government. See, e.g., Negotiations at 77. The instructions to the commission from the Commissioner of Indian Affairs, dated July 27, 1892, stated in part: “It is understood that some of these lands are very valuable and will be eagerly sought after. It is therefore suggested the agreement provide for their appraisement and sale to the highest bidder.” The Yankton commissioners apparently believed, however, that the tribe would receive more money from a single sale directly to thé government so they adopted the approach taken in Article II. See, ' e.g., S.Exee.Doc. No 27, 53d Cong., 2d Sess. at 68 (1894) (“Negotiations”).
Although a lump sum payment can in some circumstances indicate congressional intent to diminish a reservation, see, e.g., DeCoteau, 420 U.S. at 447-448, 95 S.Ct. at 1094-95, the record in this ease does not support that conclusion. The commission’s instructions, the stated desires of the Indians, and the House debate all show that a sum certain price was included for reasons [1447]*1447other than issues of jurisdiction and sovereignty.
In their briefs the signatories to the 1892 agreement state that Article XVIII has the strongest savings clause of any unallotted land sale agreement between a tribe and the government. It states:
Nothing in this agreement shall be construed to abrogate the treaty of April 19th, 1858, between the Yankton tribe of Sioux Indians and the United States. And after the signing of this agreement, and its ratification by Congress, all provisions of the said treaty of April 19th, 1858, shall be in full force and effect, the same as though this agreement had not been made, and the said Yankton Indians shall continue to receive their annuities under the said treaty of April 19th, 1858.
A number of savings clauses in other agreements also state that earlier agreements and treaties will “be in full force and effect,” but none include such a strong phrase as “the same as though this agreement had not been made,” and most include language explaining that prior treaties will remain in force so long as they are “not inconsistent” with the later agreement. See, e.g., Oregon Dept. of Fish and Wildlife v. Klamath Indian Tribe, 473 U.S. 753, 760-61, 105 S.Ct. 3420, 3425, 87 L.Ed.2d 542 (1985) (“nothing in this agreement shall be construed to deprive [the tribe] of any benefits to which they are entitled under existing treaties not inconsistent with the provisions of this agreement.”); Rosebud Sioux Tribe v. Kneip, 430 U.S. 584, 623, 97 S.Ct. 1361, 1381, 51 L.Ed.2d 660 (1977) (Marshall, J., dissenting) (benefits of existing treaties and agreements continue unless “inconsistent with the provisions of this agreement.”); United States v. Southern Ute Tribe or Band of Indians, 402 U.S. 159, 162, 91 S.Ct. 1336, 1338, 28 L.Ed.2d 695 (1971) (all treaty provisions “not altered by this agreement shall continue in force”); Dick v. United States, 208 U.S. 340, 352, 28 S.Ct. 399, 402-03, 52 L.Ed. 520 (1908) (treaty provisions “not inconsistent with the provisions of this agreement are hereby continued in full force and effect”).
Article XVIII contains no similar limitation. It does not state that only consistent aspects of the earlier treaty are to'continue. It states simply that the provisions of the' 1858 treaty are to remain in effect regardless of the contents of the agreement, “as though this agreement had never been made.”
The rules of statutory construction require that all clauses of an agreement be read together in a way that will make them consistent and give all parts force. Colautti v. Franklin, 439 U.S. 379, 392, 99 S.Ct. 675, 684, 58 L.Ed.2d 596 (1979). Article XVIII. should be read together with the other sections of the 1892 agreement to see whether all parts ean be interpreted consistently, and the unusually expansive language of Article XVIII suggests that other sections should, be read narrowly to minimize bny conflict with the 1858 treaty.
The state does not dispute the strength of the language of Article XVIII, but argues that the savings clause in this case was meant only to reassure the tribe that it would continue to receive annuities under the 1858 treaty.12 Interpreting Article XVIII to cover more than annuities would render the 1892 [1448]*1448agreement largely meaningless, it says. The treaty of 1858 required the United States to “protect the said Yanctons [sic] in the quiet and peaceable possession of the said tract of four hundred thousand acres of land so reserved for their future home.” If their possession were intended to continue “in full force and effect” after the 1892 agreement, sale of the unallotted lands would conflict with that intent by terminating the possesso-ry rights of Indians. Article XVIII should therefore be read as covering only annuities.
The record shows that the tribe had been concerned about its annuities during the negotiations, but many concerns of a more general nature were also expressed. One of these concerns was the failure of the United States to uphold its obligations under past treaties. See, e.g., Negotiations at 55, 57-58.
Article XVIII is written in broad language, stating in the first sentence that nothing in the agreement “shall be construed to abrogate” the 1858 treaty and in the second sentence that “all provisions” of that treaty shall continue “in full force and effect.” Only the second independent clause of the second sentence mentions annuities. The interpretation proposed by the state would give effect to only one of the independent clauses in one of the sentences. Other agreements specifically protected Indian annuities, but they did not use broad language apparently encompassing all treaty provisions.13 These other examples show Congress knew how to limit the. reach of an annuities provision, but it did not enact that type of limited provision in Article XVIII. Giving effect to the plain language and all parts of the article leads to the conclusion that it covers more than annuities.
It is possible to give meaning to all sections of the 1894 statute by examining them to see if they can be fairly reconciled, as the Supreme Court has directed. Colautti, 439 U.S. at 392, 99 S.Ct. at 684. The key question in interpreting the 1894 statute and agreement is whether Congress intended that the tribe’s governmental authority be transferred with the land sale. Amicus United States argues that the 1858 treaty gave the tribe governmental authority within the treaty boundaries and that Article XVIII requires that the agreement be read to preserve that right. Although the cession language in Articles I and II could be viewed as describing a transfer of tribal governmental authority as well as land, thereby changing the 1858 treaty boundaries, the narrower reading is that the 1894 act simply authorized the conveyance of real property. The Supreme Court has found the sale of lands to homesteaders not inconsistent with the preservation of existing reservation boúndaries. Rosebud, 430 U.S. at 586, 97 S.Ct. at 1362-63. The Yankton treaty of 1858 acknowledged the authority of the tribe over the reservation, and Article XVIII of the 1894 statute indicated that as much of that treaty as possible was to be preserved. The narrower reading of Articles I and II gives consistent meaning to Article XVIII and the agreement as a whole.
This court has previously given effect to a savings clause in determining that the Fort Berthold reservation was not diminished. City of New Town v. United States, 454 F.2d 121 (8th Cir.1972). The savings clause in the agreement between the Three Affiliated Tribes and the United States read:
That nothing in this Act shall be construed to deprive said Indians of Fort Berthold Indian Reservation of any benefits under existing treaties or agreements not inconsistent with the provisions of this Act.
Id. at 125. The court concluded that opening the reservation .to settlement was not inconsistent with maintaining existing reservation boundaries. Id. (citing Seymour v. Superintendent, 368 U.S. 351, 82 S.Ct. 424, 7 L.Ed.2d 346 (1962)). Although the state attacks the continued validity of New Town, it is consistent with subsequent Supreme Court precedent. See Duncan Energy, 27 F.3d at 1296-97; see also, United States v. Standish, 3 F.3d 1207 (8th Cir.1993). Article XVIII should be given due. weight in interpreting the Yankton agreement just as in New Town.
[1449]*1449Articles I, II, and XVIII may be read together to give meaning to them all, and we conclude that in combination they reveal an intent to preserve the 1858 reservation boundaries.14 Moreover, to the extent there could be any ambiguity perceived in the statute, it would have to be resolved in favor of the tribe.15 Hagen, 510 U.S. at 410-11, 114 S.Ct. at 965.
Several other articles in the agreement also have some relevance on the issue of congressional intent. For example, Article VIII reserves from sale to settlers “[s]uch part of the surplus lands hereby ceded and sold to the United States as may now be occupied by the United States for agency, schools, and other purposes ... until they are no longer required for such purposes.” An almost identical clause was considered by a unanimous Supreme Court in Solem to show that Congress foresaw continuation of the reservation there. 465 U.S. at 474, 104 S.Ct. at 1168 (“It is difficult to imagine why Congress would have reserved lands for such purposes if it did not anticipate that the opened area would remain part of the reservation.”).16
South Dakota suggests that Article XVII indicates that Congress intended to diminish the reservation. That article provided that no liquor should be sold or given away on either the lands ceded and sold to the United States or “upon any other lands within or comprising the reservations of the Yankton Sioux.”17 The district court found that this provision was included at the insistence of the Yankton Sioux, who were concerned that white saloons would attract tribal members “to the great injury of their people.” 890 F.Supp. at 882. The state argues, however, that the inclusion of such a provision shows [1450]*1450that the Indians knew that the unallotted lands would no longer be on reservation land after the sale. It cites Rosebud where the Supreme Court concluded that a similar clause in an agreement gave rise to an inference that Congress intended to diminish the Rosebud reservation in 1910. 430 U.S. at 613, 97 S.Ct. at 1376. A statute passed in July 1892 had outlawed the sale of intoxicants in Indian Country so it appeared the clause would not be needed in 1910 if the lands still were in Indian country. Act of July 23, 1892, 27 Stat. 260; Rosebud, 430 U.S. at 613, 97 S.Ct. at 1376.
The negotiations with the Yankton tribe were conducted shortly after the 1892 liquor act had passed, and there is no evidence that any party was aware of it at the time the agreement was negotiated. The Yankton agreement provided that the prohibition on liquor would continue forever, while the agreement in Rosebud was only for twenty-five years. The 1892 liquor statute would have ceased to apply if the Yankton reservation were eliminated at some future point, but the liquor provision the tribe insisted on would remain. Article XVII in the Yankton agreement is therefore not surplusage in the same manner as the liquor provision in Rosebud and is not inconsistent with an intent to preserve the 1858 boundaries. The presence of a similar alcohol clause was found not to demonstrate an intent to diminish in New Town, 454 F.2d at 127.
The state argues that one other provision in the statute ratifying the 1892 agreement supports a finding that the reservation was diminished. Congress added the provision that “the sixteenth and thirty-sixth section in each Congressional township ... shall be reserved for common-school purposes and be subject to the laws of the State of South Dakota.” Similar language in the Rosebud agreement was interpreted as having been intended to conform to the enabling act which admitted North and South Dakota to the United States. 25 Stat. 679 (1889). Under that act, the sixteenth and thirty-sixth sections in each township were granted to the state for common schools, but permanent federal reservations were excepted. Id.; Rosebud, 430 U.S. at 599-600, 97 S.Ct. at 1369-70. The Supreme Court reasoned that by using the same provision in the Rosebud surplus land act as was used in the statehood act, Congress indicated its intent to diminish the Rosebud reservation. Id. at 600-01, 97 S.Ct. at 1370. South Dakota argues that the same reasoning should be applied here.
The rationale from Rosebud has considerably less force in this ease, however, because the 1894 Yankton act makes the common school sections “subject to the laws of the State of South Dakota.” If Congress had intended to diminish the Yankton reservation, those common school sections would have been subject to the laws of the state in any event and the grant of jurisdiction would have been unnecessary. The language is at least equally consistent with a reading that Congress wished to insure that the infrastructure would exist for common schools for all future residents of the assimilated area.
South Dakota argues that analysis of the statute and the agreement is unnecessary because certain federal and state cases should control the result here. Whether the Yankton reservation was diminished or disestablished has never been squarely litigated and decided in federal court, however.18 The [1451]*1451South Dakota cases were criminal prosecutions in which the tribe was not involved and do not show Ml development of the issues or the analytical approach required by the United States Supreme Court.19 See Solem, 465 U.S. at 470, 104 S.Ct. at 1166. Moreover, the Supreme Court has indicated that federal courts are not necessarily bound by earlier state court conclusions about disestablishment issues.20
We conclude after examining the statutory language that Congress did not express in the 1894 act an intent to diminish or disestablish the reservation. Also relevant in the required analysis is review of the legislative history and the events near the time of its passage, Hagen, 510 U.S. at 410-11, 114 S.Ct. at 965, and we turn now to this review.
B.
South Dakota contends that the legislative history indicates that the unallotted lands on the Yankton reservation were restored to the public domain and that this shows Congress intended to diminish the reservation. While “the existence of [public domain] language in the operative section of a surplus land Act indicates that the Act diminished the reservation,” Hagen, 510 U.S. at 414, 114 S.Ct. at 967, there is no mention of restoring the land to the “public domain” in the 1894 act or the 1892 agreement. South Dakota claims that even though there is no public domain language in the act itself, comments on the House floor about returning reservation lands to the public domain suggest an intent to diminish the Yankton reservation. The tribe responds that the debate was inconclusive at best.
Comments in Congress can be evidence of an intent to diminish, see DeCoteau, 420 U.S. at 446, 95 S.Ct. at 1094, but the legislative history does not demonstrate such an intent here. Several surplus land sales were included in a single Indian appropriations bill in 1894, including land purchases from the Yankton Sioux, Nez Perce, Yuma, Alsea-Siletz, Coeur d’Alene, and Yakima reservations. 26 Stat. 286 (1894). South Dakota points to two instances where representatives mentioned the public domain. One stated that the various provisions in the agreements “change the methods of disposing of the lands that will become part of the public domain....” 53 Cong.Rec. 6425 (1895). A second commented that the unal-lotted lands opened by the various agreements “are not governed by the public land laws until they become segregated from the Indian lands and become in fact a part of our public domain.” Id. at 6426. Both comments were made in the context of a debate about whether the lands were to be furnished to settlers at no cost under the Homestead Act.
The comments cited by the state were made in reference to a group of agreements with some half dozen tribes. The different agreements were all included in one appropriations bill, but Congress used varying enacting sections for each.21 For example, two of the six mentioned.the public domain in the enacting section. Another explicitly referred [1452]*1452to the fact that a new boundary would have to be drawn. Floor comments about multiple agreements which differ in their distinctive language and negotiation histories are of less value in evaluating congressional intent about any individual agreement than comments dedicated to that agreement alone.
The history of the commission to the Yank-ton Sioux and its negotiations with the tribe also suggests that Congress did not intend to disestablish the reservation. The commission was instructed: “If [the Yankton Sioux] are unwilling to cede all the surplus land you will endeavor to obtain the relinquishment of such part thereof as they may be willing to part with.”22 These instructions are consistent with the mission to secure land for settlement and to expose the tribe to settlers. Had the intent been the elimination of the reservation, it would have been necessary that all surplus lands be purchased.
The state points to a number of passages from the negotiations between the commission and the tribe which it believes show that the reservation would be disestablished, but the statements are consistent with a simple sale of the surplus lands and do not necessarily imply a transfer of sovereignty. For example, one of the commissioners said to tribal members:
This reservation alone proclaims the old times and the old conditions. But even here the means of your former mode of life have vanquished [sic]. The tide of eivilization is as resistless as the tide of the ocean, and you have no choice but to accept it and live according to its methods or be destroyed of it. To accept it requires the sale of these surplus lands and the opening of this reservation to white settlement.
Negotiations at 81. The commissioner talks of a “sale” of surplus lands and the “opening of this reservation,” but makes no mention of reduction or elimination of boundaries or any surrender of jurisdiction.
In another passage relied on by the state, a commissioner stated:
The Great Father desires and seeks in this transaction the benefit of the tribe, and what you may receive in this matter will be for this tribe alone, to help elevate you to citizenship, and as soon as you become the equals and assistants of the white man in making the laws, to be near him and learn his ways, you will learn to farm, to do all kinds of business, to be citizens in the true sense of the word. It might be, after you have sold your lands, you could have this reservation organized as a separate county. If this could be done — I do not say it can — you could govern your own people in your own way, so long as you obeyed the laws of the State.
Negotiations at 48. This passage shows that possible future state jurisdiction over the Indians was contemplated, but it does not indicate when any such jurisdiction would attach and under what circumstances. The passage clearly appears to envision continuity of the reservation, with the possibility it could be transformed into a county at some later date.
The tribe argues that these comments are very weak when compared to statements made by, or to the Indians, in cases where diminishment was found. In Rosebud, for example, the tribe was specifically told that “[t]he cession of Gregory county ... will leave your reservation a compact, and almost square tract, and would leave your reservation about the size and area of Pine Ridge Reservation.” 430 U.S. at 591-92, 97 S.Ct. at 1365-66. In Hagen, the tribe was informed:
You say that [the reservation boundary] line is very heavy and that the reservation is nailed down upon the border. That is very true as applying to the past many years and up to now, but congress has provided legislation which will pull up the nails which hold down that line and after next year there will be no boundary line to this reservation.
Hagen, 510 U.S. at 417, 114 S.Ct. at 968 (internal citations omitted). In DeCoteau, a spokesman for the tribe stated:
Now that South Dakota has come in as a state we have some one to go to, to right our wrongs. The Indians have taken their land in severalty. They are waiting for [1453]*1453patents. The Indians are anxious to get patents. We are willing the surplus land should be sold. We don’t expect to keep reservation, [sic]
DeCoteau, 420 U.S. at 433, 95 S.Ct. at 1087. The Indians on these three reservations were thus clearly aware that their reservations would be smaller alter the sale of lands. Neither the commissioners nor the tribal members made like comments in this case.
The negotiations between the Yankton Indians and the commissioners sent to secure the sale of unallotted lands do not support a finding of diminishment. Despite a long series of negotiations, most of which were recorded and included in the commission’s report to Congress, there is no statement that clearly indicates that Congress intended to change the reservation boundaries or remove tribal sovereignty over the opened areas. There are also no statements by members of the tribe that demonstrate an understanding that the reservation boundaries would change.
In addition to the history of the negotiations and the legislation, there is other evidence to examine which might indicate the contemporary understanding of the 1894 act, The tribe believes the most significant piece of contemporary evidence is in an 1896 statute passed by Congress. The statute began: “Be it enacted ... [t]hat all settlers who made settlement under the homestead laws upon lands in the Yankton Indian Reservation, in the State of South Dakota, during the year eighteen hundred and ninety-five are hereby granted leave of absence from such homestead for one year....” 29 Stat. 16 (Feb. 26, 1896) (emphasis added). Section 3 of the statute extends “the time for making final proof and payment for all lands located under the homestead laws of the United States upon any lands of any former Indian reservation in the State of South Dako-ta_” Id. (emphasis added).
Congress thus continued in 1896 to refer to the unallotted lands as being in the Yankton reservation, a year after President Cleveland had opened the reservation lands for settlement. South Dakota argues that the 1896 statutory reference is entitled to little weight because the Commissioner of Indian Affairs used the word “former in a document included in the legislative history. In the statute itself, however, Congress used “former” in section 3 when referring to a number of unspecified reservations in South Dakota, but not when referring to the Yankton reservation in section 1.,
The state argues that other contemporaneous evidence indicates' that the reservation was diminished. For example, it points to several statements by the Commissioner of Indian Affairs as being particularly relevant. Shortly after passage of the 1894 act, the commissioner stated that the Yankton agreement in 1892 and two others would result in a significant amount of land being “restored to the public domain.” Annual Report of the Commissioner of Indian Affairs 26 (1894). Two years later the commissioner referred to the “former” Yankton reservation. H.R.Rep. No. 100, 54th Cong., 1st Sess. at 2 (1896). These appear to be isolated references, however. The tribe’s Yankton Sioux history expert testimony at trial was unrefuted that in the many thousands of documents he had read regarding the reservation, references to the former reservation or lands originally within the reservation were infrequent.
South Dakota also states that it began exercising jurisdiction over the areas no longer held in trust by the United States shortly after the lands were opened. An 1895 criminal case, State v. Andrew War, First Judicial Circuit Court, Charles Mix County, supports this claim, as do several other cases cited by the state.’- The exercise of jurisdiction by a state over opened lands can be an indication of congressional intent, but it is not dispositive. See Solem, 465 U.S. at 472, 104 S.Ct. at 1167.
Some other evidence is simply inconclusive. Both sides introduced a number of maps, many of them from within several years of the opening of the lands. These maps ultimately prove little except that there was some confusion both inside and outside the government as to the status of the reservation. The General Land Office of the Department of the Interior showed the reservation with only a dotted line on a 1901 map. The legend did not specify what a dotted line [1454]*1454meant, but it is not the demarcation shown for a reservation. On the other hand the Bureau of Indian Affairs, also in the Interior Department, continued to show the outline of the reservation on its maps. The type of outline used was identified in the legend to signify an Indian reservation, but the Yank-ton reservation was left unshaded while some other reservations were shaded. Study of the pattern of shading on these maps suggests that reservations opened to settlement were left unshaded. Because of these conflicting treatments and because an opened reservation is not necessarily diminished, these and similar maps are not particularly helpful.
Commercial maps have also differed. For example, The Atlas of Charles Mix County, South Dakota, published in 1906, does not appear to show the reservation. Exh. 631. A very detailed map of South Dakota' in one 1895 atlas does show it. Rand McNally World Atlas 277 (1895). The confusion- is perhaps best exemplified by Andrees’ Hand Atlas, published in Germany. In both the 1899 and 1904 editions of the German atlas, a map of the United States shows the reservation (pages 160-61 in both editions), while a regional map on the next, plate does not (pages 162-63).
These examples of confusion about the status of the lands are not enough to show that Congress expressly intended to diminish the reservation, and the 1896 statute is more probative of congressional intent than this more attenuated evidence. The statute is a statement by Congress itself and .should guide the appraisal of the contemporaneous evidence. It suggests that Congress did not intend to diminish the Yankton reservation.
IV.
The pattern throughout the twentieth century is similar to the contemporaneous evidence. Congress has continued to refer to the reservation as a continuing entity, but the treatment by other governmental bodies is mixed. Although less persuasive than evidence from the time surrounding an act’s passage, later evidence is still relevant. Hagen, 510 U.S. at 410-11, 114 S.Ct. at 965.
Congress has repeatedly referred to the Yankton Reservation as ongoing. In 1920, for example, Congress provided “[t]hat the Secretary of the Interior be ... authorized. and directed to convey to the trustees of the Yankton Agency Presbyterian Church, by patent in fee, the following-described premises situate [sic] within the Yankton Indian Reservation, county of Charles Mix, State of South Dakota.” 41 Stat. 1468 (1920) (emphasis added). In 1932, Congress divided the United States District Court for the District of South Dakota into four divisions. “The territory embraced ... in the counties of Aurora, Beadle, ... Charles Mix, ... Yankton, and in the Yankton Indian Reservation, shall constitute the southern division of said district.” 47 Stat. 300 (1932) (emphasis added). More recently, a water project approved by Congress will “irrigate not more than approximately three thousand acres of Indian-owned land in the Yankton-Sioux Indian Reservation_” Reclamation Projects Authorization and Adjustment Act of 1992, Pub.L. No. 102-575 § 2005(b) (1992) (emphasis added).
The state has not directed the court to a single enactment of Congress in which a reference was made to indicate the reservation had been diminished. The statutory references demonstrate that Congress believes the Yankton reservation continues to exist.
The executive branch has been less consistent, but there is considerable evidence from it in support of an undiminished reservation. In its brief the tribe points to testimony before Congress by the superintendent of the Yankton Agency in 1914 that the reservation was “[a]bout 26 by 35 or 36 miles,” the area encompassed by the 1858 boundaries. In 1916, President Woodrow Wilson ordered “that the trust period on the allotments of Indians on the Yankton Sioux Reservation, South Dakota, which expires during the calendar years 1916 and 1919, be, and is hereby, extended for a period of ten years from dates of expiration, with the exception of the following _” (Exec.Order April 20,1916).
[1455]*1455Perhaps the foremost authority on federal Indian law, Felix Cohen wrote an opinion in 1941 while he was Acting Solicitor of the Department of the Interior that concluded the reservation was intact. It read in part:
The circumstances which influenced the Indian Office decision [that the reservation had been diminished] are the large amount of reservation land which has been fee patented and the existence of towns within the reservation. These circumstances may be persuasive in reaching an administrative conclusion, but I cannot agree with the conclusion as a matter of law.
The agreement of 1892 provided for the sale of such lands within the reservation as were not allotted or used for designated purposes. It did not provide for the sale of a particular designated part of the reservation. The act should be distinguished from other cession acts which ceded a definite part of the reservation and treated the remaining area as a diminished reservation. The lands allotted on the Yankton Reservation were scattered over all the reservation_ Since the 1892 agreement there has been no redefinition by Congress of the Yankton Reservation nor determination that the reservation no longer exists. On the contrary, the reservation was referred to as a still existing unit in the acts of April 29, 1920 (41 Stat. 1468) and June 11,1932 (47 Stat. 300).
Letter of August 7, 1941, Opinions of the Solicitor, Department of the Interior 1063 (1979).
Others within the executive branch have taken varying positions. In 1969 an Associate Solicitor wrote that “the effect of the 1894 Act was to eliminate reservation boundaries and terminate the tribe’s authority to establish a tribal court.” Memorandum M-36783 from Associate Solicitor, Indian Affairs, to Commissioner of Indian Affairs, 1 (September 10, 1969).23 An employee of the Bureau of Indian Affairs in its Aberdeen, South Dakota office testified at trial that his office considers the 1858 boundaries to be intact, and the 1990 census includes figures for the “Yankton Reservation” as defined by the 1858 boundaries. See, e.g., Bureau of the Census, U.S. Dep’t of Commerce, Pub. No. 1990 CPH-1-43, Summary Population and Housing Characteristics — South Dakota 175 (1991). The United States as amicus In this case (and also a party to the treaty of 1858 and the 1892 agreement) argues that “the 1892 Agreement, as ratified by Congress, did not diminish or disestablish the exterior boundaries of the Yankton Sioux Reservation.”
The state government has quite consistently exercised various forms of governmental authority over , the opened lands on the Yank-ton reservation. State courts have exercised criminal jurisdiction over Indians on nontrust lands without objection from the tribe until recently. See, e.g., supra note 19. The state has also exercised some civil jurisdiction, at least over divorces between tribal members. See, e.g., Redbird v. Redbird, First Judicial Circuit Court, Charles Mix County (1916). The state has also played a significant regulatory role in mining, underground storage tanks, agriculture, air emissions, solid and hazardous waste, and other environmental activities in the area. The county and municipalities employ law enforcement personnel and maintain over 500 miles of roads within the 1858 boundaries, while the Bureau of Indian Affairs maintains only 20 miles of roads.
The state’s treatment of the reservation has not been uniform, however. Ronald Cat-lin, a state witness and an employee of the South Dakota Department of Game, Fish, and Parks recalled seeing a memorandum instructing state employees how to refer to the reservation. Catlin remembered that the memo was written by Governor William Janklow sometime between 1978 and 1986 and directed employees to refer only to the “former Yankton Sioux Reservation.” A reasonable inference to be drawn is that at least some state employees had been referring to the reservation as if it still existed'.
The state argues that the tribe itself has not asserted jurisdiction over the opened br-[1456]*1456eas and that some documents indicate that tribal members believed that the reservation boundaries had been reduced. The tribe's 1932 constitution was silent on the issue of jurisdiction, but the amended 1962 constitution claimed jurisdiction over “all original Tribal lands now owned by the Tribe under the Treaty of 1858.” The tribe presented no evidence that it has attempted until recently to exercise civil, regulatory, or criminal jurisdiction over nontrust lands. Undisputed evidence at trial indicated that the tribe’s effectiveness at self-government has also varied considerably over time.
Modem maps and atlases seem to show the reservation as extending to the 1858 boundaries. See U.S. Department of Commerce, 1990 Census of Population: Social and Economic Characteristics, South Dakota G-6 (1993); U.S. Department of the Interior Bureau of Indian Affairs, Indian Land Areas (General) [map] (1987); National. Geographic Historical Atlas of the United States, 47 (Centennial Edition 1988) (see also, loose map entitled “Northern Plains” included with the atlas); Waldman & Braun, Atlas of the North American Indian 196-97 (Facts on File Publications 1985).
Considering all of the evidence submitted by the parties and amici regarding the subsequent history of the reservation, we cannot say that the surrounding circumstances are “fully consistent with an intent to terminate the reservation, and inconsistent with any other purpose.” See DeCoteau, 420 U.S. at 448, 95 S.Ct. at 1095.
South Dakota argues that “[t]he Supreme Court has decreed that even in a case where de jure diminishment may not have occurred, ‘de facto’ diminishment may nonetheless have occurred.” The tribe and the United States respond that de facto diminishment has never been applied in the absence of congressional intent to diminish.
Solem contains the Supreme Court’s most complete discussion of de facto diminishment. It recognized there that:
who actually moved onto opened reservation lands is also relevant to deciding whether a surplus land act diminished a reservation. Where non-Indian settlers flooded into the opened portion of a reservation and the area has long since lost its Indian character, we have acknowledged that de facto, if not de jure, diminishment may have occurred.
Solem, 465 U.S. at 471, 104 S.Ct. at 1166. South Dakota argues that this permits a finding of diminishment even in the absence of congressional intent.
The Court in Solem cautioned, however, that subsequent demographic data are only “one additional clue as to what Congress expected would happen once land on a particular reservation was opened to non-Indian settlers.” Id. at 471-72, 104 S.Ct. at 1167.
When both an Act and its legislative history fail to provide substantial and compelling evidence of a congressional intention to diminish Indian lands, we are bound by our traditional solicitude for the Indian tribes to rule that diminishment did not take place and that the old reservation boundaries survived the opening.
Id. at 472, 104 S.Ct. at 1167. Subsequent demographic data and jurisdictional history regarding the opened lands may therefore be useful evidence of congressional intent,' but cannot substitute for it.
' The demographic facts related to the Yankton reservation are somewhat incomplete. Between 1890 and 1900, the population of Charles'Mix County doubled, but it is not clear from the census data how many of those people settled on the open lands within the 1858 boundaries.24 Of the 8,498 persons in the county in 1900, 1,483 were Indians. Assuming that people were distributed evenly throughout the county (which is not clear from the record), roughly 4,000 people would have lived within the 1858 boundaries. The [1457]*1457Indian population would have made up about 40 percent of the reservation.
Demographic shifts that happen soon after an act is passed would appear to be stronger evidence of congressional intent than later population changes because those closer in time might have been better anticipated by Congress. The contemporaneous evidence suggests that the area did not lose its “Indian character,” see Solem, 465 U.S. at 471, 104 S.Ct. at 1166, because more than 53 percent of the land was allotted to tribal members who composed at least 40 percent of the population. After 1900 the Indian population apparently declined somewhat. Southern Missouri, 890 F.Supp. at 887.
There is some dispute in the record about precisely how many Yankton Sioux now live within the 1858 boundaries. According to the 1990 census, there were 1,994 American Indians and 4,275 non-Indians living on the ‘Yankton Reservation,” which the Census Bureau defined as being within the 1858 boundaries.25 Bureau of the Census, U.S. Dep’t of Commerce, Pub. No.1990 CP-1-4S, General Population Characteristics — South Dakota 29 (1992). The tribe claims that the Census data do not accurately reflect the population of the area and that some 3,400 enrolled members of the tribe resided on the reservation as of 1993. These two sets of figures indicate that between 32 and 44 percent of the people within the 1858 boundaries are Indians.26 (In contrast, the 1990 census reports that of the Indians living in Charles Mix County, only eight live outside the 1858 treaty boundaries.)
Finally, the evidence shows that the Indian population and influence in the area is increasing quite rapidly, a trend which appears likely to continue. The tribe opened the Fort Randall casino in 1991 which has provided both jobs and financial resources to tribal members and is apparently now the largest employer in Charles Mix County. The tribe has also announced its intention to use some of the casino proceeds to reacquire title to lands which have passed from Indian hands since 1894. Meanwhile the non-Indian population is decreasing.
The historical and demographic evidence does not show that Congress intended to change the 1858 boundaries. Only Congress can reduce or eliminate a reservation, see, e.g., Solem, 465 U.S. at 470, 104 S.Ct. at 1166, and it is “totally inappropriate” to rely only on de facto diminishment to reduce the size of a reservation. Duncan Energy, 27 F.3d 1294, 1298 (8th Cir.1994). The Yankton Sioux make up a significant portion of the population of the treaty area, and their numbers and economic influence are increasing. Thus, even if de facto - diminishment were possible’in spite of the lack of substantial evidence of congressional intent in the 1894 act and its legislative history, see Solem, 465 U.S. at 472, 104 S.Ct. at 1167, the record would not support it here.
V.
In sum, application of the factors deemed relevant by the Supreme Court leads to the conclusion that Congress intended by its 1894 act that the Yankton Sioux sell their surplus land to the government, but not their governmental authority over it. Close examination of the agreement, the act, and the historical record does not reveal the “[s]ub-stantial and compelling evidence of a congressional intention to diminish Indian lands” necessary for disestablishment or diminishment, but instead indicates the 1858 treaty boundaries were to be preserved. Solem, 465. U.S. at 472, 104 S.Ct. at 1167. The judgment of the district court is affirmed.