Stages of Construction
The earth walls were built over a period of approximately three hundred years and used for a couple of hundred years beyond that. American Indians used the shoulder bones of deer and elk, split elk antler, clam shell hoes, and digging sticks to loosen the earth. They moved the earth in woven baskets that held about 40 pounds. If archaeologists' interpretations are correct, the earth walls were built in three stages. The South Fort was built first, followed by the Middle Fort. The North Fort and Parallel Walls were built last, between AD1 to AD200.
Archaeologists estimate that between one and three feet of soil have eroded from the earthworks since they were built. Today we stress preservation through education. In order to preserve the past for the future, we must care for it today. It is for this reason that visitors are not permitted to walk on the earth walls or mounds.
Early archaeologists once thought the Crescent Mounds served as the best fortified area of the site due to the shape of the walls. Today, they think this gateway served to funnel people through for ceremonial purposes, probably toward the Great Gateway, which is the entrance to the South Fort.