The Porteous Mound is an earthen ceremonial mound built between 800 B.C. and 500 A.D. by prehistoric people who lived in this valley. Unlike most other mounds in Ohio, which were used for burials, this mound was used for ceremonial purposes. It was first excavated in 1896 by W. K. Moorehead, when it measured 120 feet in diameter and 23 feet high.