Together with the Hunkpapa and Sihasapa bands, the Standing Rock Sioux Tribe is part of what was known as the Great Sioux Nation. The peoples were highly decentralized. In 1868 the lands of the Great Sioux Nation were reduced in the Fort Laramie Treaty to the east side of the Missouri River and the state line of South Dakota in the west. The Black Hills, considered by the Sioux to be sacred land, are located in the center of territory awarded to the tribe.

In 1874, in direct violation of the treaty, General George A. Custer and his 7th Cavalry entered the Black Hills and discovered gold, starting a gold rush. The United States government wanted to buy or rent the Black Hills from the Lakota people, but led by their spiritual leader Sitting Bull, they refused to sell or renits superior resources was soon able to force the Native Americans to surrender, primarily by attacking and destroying their encampments and property. The Agreement of 1877 (19 Stat. 254, enacted February 28, 1877) officially annexed Sioux land and permanently established Native American reservations. Under the Agreement of 1877 the U.S. government took the Black Hills from the Sioux Nation.t their lands. The Great Sioux War of 1876 was a series of battles and negotiations that occurred between 1876 and 1877, with the Lakota Sioux and Northern Cheyenne warring against the United States. Among the many battles and skirmishes of the war was the Battle of the Little Bighorn, often known as Custer's Last Stand, the most storied of the many encounters between the U.S. army and mounted Plains Native Americans. It was an overwhelming Native American victory.