Fort Randall once stood as an isolated fort on the edge of the frontier, but by the time North and South Dakota became states in 1889 it had become an interior post surrounded by settlements and had outlived its usefulness. In the 1870s, the Black Hills Gold Rush and the arrival of the railroads brought the Great Dakota Boom, during which the European-American population increased dramatically. The railroads also made the chain of forts around the former Sioux lands unnecessary because troops and supplies could be moved quickly throughout the West. Fort Randall was officially abandoned in 1892, and in 1895 its buildings were sold at auction, with most dismantled or moved elsewhere. The last company to leave the post was composed entirely of Native Americans commanded by two white officers.