First called White River Agency, this agency was established in 1876 for the Sicangu and Oohenunpa bands of Lakota living under the control of Crow Creek agency. It was first located on the western side of the Missouri River ten miles below Crow Creek. In 1876, it was moved to the mouth of American Crow Creek, twelve miles below the old site. Lower Brule and Crow Creek Agencies were consolidated in 1882, then divided again in 1896.
Early records document nine bands located at Lower Brule. The following headmen, who signed the 1868 Fort Laramie treaty, were leaders of those early bands: Iron Nation, Medicine Bull, One Who Kills the White Buffalo Cow, Little Pheasant, White Buffalo Cow That Walks, Brave Heart, Wounded Man, Gourd Ear Rings, and Iron White.
Today the agency is located on the west bank of the Missouri river in south central South Dakota in Stanley and Lyman counties with a land base of 132,601 acres. Lake Sharpe and Big Bend Dam are popular tourist attractions.