The mid–seventeenth through the late nineteenth centuries were times of tremendous change for the Native peoples of the Plains. They seized new opportunities presented by the arrival of Europeans and by the subsequent expansion of settlers from the United States and Canada into the trans-Mississippi West. Native peoples adapted new technologies to their own needs, elaborated and transformed their basic social and cultural institutions, and helped to create a multiethnic society in the West. For some Native groups the new opportunities enabled expansion and domination of neighboring peoples. The histories of others were shaped by a sometimes unsuccessful struggle to resist domination and dispossession. Through time, alliances shifted, as did the balance of power. Eventually, the Native peoples were overwhelmed by American and Canadian expansion and forced onto small reserves where they continued to struggle to hold on to the things they valued and to determine for themselves how they would change in adapting to new circumstances. Throughout the centuries, the decisions they made helped shape North American history.

Some of the Native peoples who occupied the Plains when Europeans first arrived in the mid–sixteenth century had been there for several hundred years or longer. Others were more recent immigrants. Over the next two centuries, more groups moved into the region, peoples who were fleeing wars among Native groups east of the Mississippi that had been brought on by European rivalries. The Great Plains region extended west from the lowland river bottom systems of the Missouri and Lower Mississippi, and gradually ascended in elevation through the grasslands, to the foothills of the Rocky Mountains. There were two adaptations to the Plains region: riverine horticultural villages, situated along the Missouri and its tributaries and along the other rivers that flowed east into the Lower Mississippi, and nomadic hunting bands that ranged in the uplands west, southwest, and northwest of the Missouri as far as the Rocky Mountains.

The riverine horticulturalists included both speakers of Caddoan languages, who had come into the Plains from the southeast about A.D. 900, and groups whose languages belonged to the Siouan family, who had moved to the Missouri from the Upper Mississippi region subsequent to the Caddoan arrival. The Caddoan peoples, the Caddos, Wichitas, Pawnees, and Arikaras, were settled on the central and southern Plains along the tributaries of the Lower Mississippi and the Lower Missouri.