The Great Sioux Reservation was an Indian reservation created by the United States through treaty with the Sioux, principally the Lakota, who dominated the territory before its establishment. In the Fort Laramie Treaty of 1868, the reservation included lands west of the Missouri River in South Dakota and Nebraska, including all of present-day western South Dakota. The treaty also provided rights to roam and hunt in contiguous areas of North Dakota, Montana, Wyoming, and northeast Colorado.