As a result of the Treaty of Fort Laramie in 1868, all land from the Bighorn Mountains down to South Dakota Territory, including Black Hills was recognized as part of the Great Sioux Reservation and it was set aside for their exclusive use. The agreement was signed between the United States and several bands of Lakota people, Yanktonai Dakota and Arapaho Nation.
However, when gold was found on Black Hills, the federal government began a campaign to expel the Native Americans from the territory. To this day, the ownership of Black Hills is still an ongoing legal dispute between the United States government and the Sioux.