The growing demands of the whites to attain the Indian Territory for themselves prompted the Concentration Policy in 1851. Each tribe was designated its own individual reservation arranged by biased whites called treaty chiefs. This scattered the tribes which made them easier to control and allowed whites to take over desirable lands. In 1867, Congress established an Indian Peace Commission who wanted to move the Plains Indians into two large reservations in Oklahoma and the Dakotas.
Native American resistance rose as fighting started up in eastern Colorado, where the Arapaho and Cheyenne had conflicts with the white miners settling in the area. Groups of Natives worked to regain lost territory by attacking stagecoach lines and settlements. The whites responded by gathering a large territorial militia. A band of peaceful natives under Chief Black Kettle camped Fort Lyon on Sand Creek in 1864 for protection. Regardless, Colonel J.M. Chivington led a volunteer militia force to the camp and massacred 133 people.
Native American resistance gained a large following again in 1875 with the Sioux leaving their reservation in the northern plains. The native warriors congregated in Montana under Crazy Horse and Sitting Bull to face three army columns under George A. Custer. The Battle of the Little Big Horn in 1876 the natives surrounded Custer. However, the power of the Sioux was weakened and the native leaders accepted defeat.
Along with the U.S. Army, white vigilantes also inflicted extensive violence upon the Native Americans through Indian hunting. Whites created a sport in tracking down and killing Natives. Hunters received bounties, killed as revenge for Native raids, or were set on the goal of eliminating the tribes. In California, hunters killed about 5,000 Indians between 1850 and 1880. This contributed greatly to the reduced Indian population before the Civil War.
As white demand for buffalo became more prevalent, white settlers and travelers killed an abundance of buffalo at a quick rate. Buffalo were also often obstacles to railroads and were shot at. By 1875, the southern herd of buffalo was basically extinct. This was a major factor in weakening the Native Americans because the buffalo provided the economic foundation of their way of life.