The Plains Indians were those tribes of Native Americans who lived on the Great Plains of North America. At the height of their cultures, their main source of food was the large herds of American bison. Hunting was not only the main activity of Plains Indians but was a central part of their religion.Their thinking and culture was formed from the natural environment they lived in. Up to the 1500s, tribes lived on the edges of the Great Plains. They were farmers and hunter-gatherers. From autumn to spring they raised crops. During the summers they went out onto the Great Plains to hunt bison on foot.