Sioux War Preparation, 1907, Edward S. Curtis.

A series of conflicts raged as white settlers encroached upon Sioux land, beginning with the Grattan Massacre in 1854 near Fort Laramie, Wyoming. Conflicts continued until the military began its Pine Ridge Campaign from November 1890 to January 1891, the last major conflict with the Sioux. This lopsided engagement, which involved almost half the infantry and cavalry of the Regular Army, caused the surviving warriors to lay down their arms and retreat to their reservations.