"The incorporation of the West into the national economy spelled the doom of the Plains Indian and their world," Eric Foner wrote. This sentence sums up everything pertaining to the impact of expansion to the West on the Native Americans.
As Settlers moved westward in the 1850's, the Army and the Plains Indians began a decades long conflict that would end with the destruction of the Indians way of life.
In 1879, two years after surrendering to the US Army, Chief Joseph of the Nez Perce Indians spoke in Washington and said "Treat all men alike, give them the same law...let me be a free man...". This would not be the case. The surviving Nez Perce Indians were placed on a reservation in Washington Territory, where Joseph continued until his death to petition Washington DC, that his people could return to their native Oregon lands.
The Americans caused the Indians to change their way of life. They wanted the Indians to conform to white man's ways of dress, school and religion. Boarding schools were established by the Bureau of Indian Affairs to remove the Indian children from the negative influences of their parents and tribes and in order to educate them in white ways.
American Citizenship was offered to the Indians if they left the tribal life and assimilated to the American way. The change of the Plains Indian is seen in a picture titled "Luther Standing Bear (1879)" on www.wwnorton.com. The picture shows him wearing a traditional Indian head dress with American trousers and a button down, collared shirt. He is shown standing next to an American man in a suit with several other well dressed Americans in the background of the picture.
The Indians life was dramatically changed. They could no longer live a peaceful life on the plains as had been their way, but were forced to change to the ways of the white man or face punishment or even death.