The Sioux can be found throughout the northern Plains, including North and South Dakotas, northern Nebraska, eastern Wyoming, and southeastern Montana. The arrival of white Americans following the Louisiana Purchase lead to an end to native Sioux life due to the depletion of the buffalo. There are three native Sioux dialects, Dakota, Lakota and Nakota. Biggest and most famous of these is Lakota.
Sitting Bull-- A Hunkpapa Lakota chief and holy man under whom the Lakota tribes united in their struggle for survival on the northern plains, Sitting Bull remained defiant toward American military power and contemptuous of American promises to the end. [PBS.org]
Sitting Bull, Lakota Sioux. "It is through this mysterious power that we too have our being, and we therefore yield to our neighbors, even to our animal neighbors, the same right as ourselves to inhabit this vast land."