Atsina.

The ethnological origins of the Atsina, or White Clay People, are mysterious. The Atsina, also known as the Gros Ventre, once belonged to an Algonquian parent nation that included the Arapaho. Until the seventeenth century, the Arapaho-Atsina hunted, gathered, and perhaps planted near the Red River of Minnesota. In the late seventeenth or early eighteenth century, the Atsina broke off from the Arapaho and moved northward and westward to the Eagle Hills in Saskatchewan. The Atsina probably subsisted by gathering and pedestrian buffalo hunting, although they also planted tobacco. In the middle of the eighteenth century, the Atsina acquired horses and became equestrian buffalo hunters. In the late eighteenth century, the Cree and Assiniboine pushed the Atsina from Saskatchewan southwest to the Upper Missouri River.