Horn Mound is a Native American earthwork near Tarlton in eastern Pickaway County, Ohio, set beside a stream and unusually isolated from other prehistoric sites. It is believed to have been built by the Adena culture, linking it to one of Ohio’s earliest and most important traditions of burial mounds and ceremonial earthworks. Its importance rests especially on its preservation: despite some erosion risk from the nearby stream, it appears to have avoided major human disturbance. That relatively pristine condition makes Horn Mound a promising archaeological site, a status recognized by its listing on the National Register of Historic Places in 1974.