The mound walls of the Old Stone Fort enclose a 50-acre area with few signs of housing, food storage, or artifacts, a pattern typical of hilltop enclosures of the period that supports the conclusion that native peoples used the site for ceremonial purposes at special points in the calendar. Conclusions about activities there may depend on patterns in the arrangement of the mounds and on gradually increasing knowledge of prehistoric American Indian belief patterns. The Old Stone Fort stood within an ecosystem shaped by seasonal cycles that ancient people used, in the Highland Rim transition zone of prairie edge environment, elevation change, and associated river valleys. This environment offered a rich resource base of wild game, natural foodstuffs, and the beginnings of agriculture. Until early historic times, the Barrens of the Highland Rim plateau were a prairie grassland environment, and together with the escarpment of the low plateau, its rivers, and its waterfalls, the area formed an environmental boundary zone attractive to American Indians in many ways.