Prehistoric Hopewell Indians built these earthworks nearly 2000 years ago. Although early settlers thought the walls were a fort, archaeologists now believe the site was used primarily as a religious and social center, and some walls and mounds may have functioned as astronomical calendars. The Hopewell occupied the major river valleys of southern Ohio, where they built hilltop enclosures, geometrically shaped earthworks, and mounds, before their culture disappeared for reasons still unclear about 500 to 600 AD. A second major group associated with this site lived here between 1200 and 1450 AD, supporting themselves by growing corn, beans, and squash as well as by hunting, fishing, and gathering wild plant foods. They established one community nearby along the Little Miami River and another within the South Fort portion of the enclosure. Although this later culture did not build the earthworks, it was the first culture archaeologists discovered at the site, and both the culture and the site came to be known as Fort Ancient.