The white settlers had little interest in the semiarid land assigned to the Sioux under the Treaty of 1868 and, for a time, the Indians enjoyed their domain in relative peace. However, when rumors spread that the Black Hills of the Dakota Territory were rich in gold, miners and newspapers wanted to organize prospecting parties. At first the government discouraged attempts to trespass upon the Sioux land, but under the pressure of public opinion, the Army in 1874 sent the Seventh Cavalry Regiment, commanded by General George A. Custer, to explore the Hills. With reports that gold had indeed been found by Custer, all hope of preserving the Sioux treaty vanished. Miners flocked to the area despite attempts by the government to keep them out; by 1876, the Black Hills had been officially removed from Sioux control.

The story of the expedition and its effect on relations with the Sioux is told from government documents, including much new material from the National Archives, and from newspaper correspondents' reports and previously unpublished journals. William Illingworth's original photographs of the expedition, reproduced here, were almost as influential as reports of the expedition in luring prospectors to the Black Hills.