The Adena Culture was a Pre-Columbian Native American culture that existed from 1000 B.C. to 100 A.D. during the Early Woodland Period throughout present-day Ohio and neighboring states. The Adena people were Athens County's first known residents, and their culture in the county can be traced between 88 B.C. and 100 A.D. Adena populations were scattered along the Hocking River and constructed mounds like this one. The Plains was the second largest center of Adena activity in Ohio and had the third largest concentration of Adena burial mounds and circular enclosures in the Eastern United States. The burial mounds contain remains, and theories hold that the circular enclosures may have served as sports arenas, clan initiation sites, or places of religious significance. When settlers arrived on The Plains in the 1800s, they found 30 earthworks, including conical mounds and circular enclosures, but only six mounds still exist today.