The Fort Laramie Treaty of 1868 was a stunning success for the Lakota people. Having routed the United States Army in a two-year campaign, the Lakota secured a 25 million acre tract of land that covered half of present-day South Dakota, known then as the Great Sioux Reservation. They were to be the sole stewards of this land; settlers were not permitted to occupy it “without the consent of the Indians,” and the United States Army would help to enforce this agreement. Any changes to the arrangement required the support of three fourths of adult Lakota men. At the time, it seemed that the problems that had plagued the Great Plains—constant warfare and violence over land and resources—were settled. Few could have predicted what would happen next.

In September of 1873, the collapse of railroad baron Jay Cooke’s investments caused a financial panic. Although the panic was the result of years of unregulated speculation, settlers in Dakota Territory believed the solution to the economic crisis was a lack of gold. This was a problem they could solve. They claimed that the Black Hills, a spiritual center for the Lakota that was also rich in natural resources, contained enough gold to revive the economy and save the nation. Under the pretense that they needed to build a new fort, General Philip Sheridan of the Army ordered a reconnaissance mission of the Black Hills in the summer of 1874. Army Lieutenant Colonel George Armstrong Custer led nearly 1,200 men into the Black Hills, which few eastern Americans had ever seen before. While reports differed on the extent, all agreed on one important finding: the Black Hills did, in fact, contain gold. Two engineers with the Army wrote the official report. “The gold-hunters were very busy all day,” they noted.

Word of the treasure in Dakota Territory soon spread across the nation, as newspapers hailed the Black Hills as a new “El Dorado.” Gold-seekers began to move into the Black Hills in defiance of the Army. Though the federal government planned to pressure the Lakota into selling the land, the Army continued to prevent illegal incursions. An article in the Yankton Daily Press and Dakotaian from April of 1875 described how the Army broke up a camp of prospectors and escorted them off Lakota land. The Army removed them so quickly that the miners lost half their cattle. They were, however, allowed to keep “a sufficient amount of… gold and silver.” When incursions continued, General Sheridan threatened to burn the wagon trains of anyone caught on Lakota land. Local writers retorted that the Army’s efforts would come to naught: miners would soon overwhelm the Army “like the Grasshoppers of Kansas,” an interesting choice of metaphor given the destruction that grasshoppers previously wrought in the area.

Their predictions proved true. Despite the Army’s presence, more than fifteen hundred miners camped in the Black Hills by August of 1875. With the threat of another violent Indian war looming, President Grant held a meeting behind closed doors in which he announced to his generals a new policy. While the government would officially continue to ban miners from the Black Hills, the Army would no longer enforce the ban. As General Sheridan wrote in a confidential letter to a colleague, “No fixed resistance should be made to the miners’ going in…. Will you therefore quietly cause the troops in your Department to assume such attitude?” An influx of settlers, government officials believed, would force the Lakota to sell the Black Hills and resolve the matter forever.

Or it would cause a war. In the 1875 report of the Commissioner of Indian Affairs, Dakota agents warned that the Lakota were furious with the “lawless invasion of the Black Hills.” Even Red Cloud, a Lakota leader who had become an advocate of peace, refused to talk with government officials. Meanwhile, Sitting Bull and Crazy Horse continued to lead thousands of “non-treaty Indians,” or Lakota who rejected reservation life. When they ignored orders to report to the reservation by the end of January, the Army declared them to be hostile and began to pursue the non-treaty Lakota. The 7th Cavalry tracked them down in June 1876. The Lakota warriors and their Cheyenne and Arapaho allies killed every soldier in the regiment, including their commander, George Armstrong Custer, who had led the original reconnaissance mission into the Black Hills just two years earlier.

The Indians’ victory was short-lived. While the Army pushed the militant Lakota north toward Canada, Congress attached rider 19 Stat. 254 to an Indian Appropriations Act, which forced Lakota on the Great Sioux Reservation to sell the Black Hills or lose the food guaranteed to them by the 1868 Treaty of Fort Laramie. To this day, the Lakota know this as the “Sell or Starve Act.” Only one in ten adult Lakota men agreed to the sale. Despite the legal requirement of three in four adult men, Congress ratified the sale in February of 1877.

In the 1870s, history moved in a violent and destructive direction for the Lakota. This was by no means inevitable. There were many possibilities, not least of which was a preservation of Lakota land and resources through the lawful support of the United States Army. It’s impossible to know what would have happened under these circumstances; miners might have continued to push into the Black Hills, just as Congress might still have pushed for illegal land sales. With the Army’s support, however, the Lakota would have had an honest chance at that ever-elusive principle: human self-determination.

On December 4, 2016, the Lakota won a major victory when the Army Corps of Engineers agreed to prevent the construction of an oil pipeline just North of the Standing Rock Sioux Reservation. The Lakota did so by rallying support from around the nation, including hundreds of native nations and thousands of veterans. With increasingly bleak climate news, they claim the victory is important not only to their health but to the survival of the planet. The oil company is challenging the decision, and the next administration is considering the dissolution of reservations altogether in order to open the land to private drilling. Today, as in 1875, it is unclear which direction history will move.