Here we have the status of "assimilation of American Indians" as seen by Richard F. Burton circa 1860:
In 1854, when Nebraska was admitted into the Union, there were, as nearly as can be estimated, 10,000 Indians on reservation & in the Territory, the greater portion of them living in the eastern part, in permanent villages, along the Missouri and Platte Rivers, and their tributaries, while in the northwestern part there were several roving bands of the great Sioux nation, of whom those in the eastern part stood in mortal fear.