What were the purposes of the earthworks built by cultures of eastern North America

The Eastern Woodland Culture consisted of Indian tribes occupying the eastern United States and Canada. The Eastern Woodlands were temperate climate regions about from the Atlantic to the Mississippi River and involved the Great Lakes. A bulk of Eastern Woodlands tribes spoke Iroquoian or Algonquian. The Iroquois preachers involved the Cayuga, Mohawk, Oneida, Onondaga, Seneca, and Huron. The Iroquoian tribes were essentially deer hunters but they also planted corn, squash, and beans, they found nuts and berries, and they fished.