サンドクリークの虐殺
The Sand Creek massacre of Cheyenne people on November 29, 1864 intensified Indian reprisals and raids in the Platte River valley. (See Battle of Julesburg) After the raids, several thousand Sioux, Cheyenne and Arapaho congregated in the Powder River country, remote from white settlements and confirmed as Indian territory in the 1851 Treaty of Fort Laramie.