river rising in Auglaize county, west-central Ohio, U.S., and flowing southeast past Columbus, Circleville, and Chillicothe, joining the Ohio River at Portsmouth after a course of some 230 miles (370 km). Griggs (built 1908) and O'Shaughnessy (1925) dams, both near Columbus, impound narrow reservoirs for water supply. Tributaries include the Olentangy River and Big Walnut Creek. Hoover Dam (1955), on the latter, created another reservoir near Columbus. The rich limestone soils of the river valley are exceptionally fertile. Scioto probably comes from the Iroquoian word for “deer.”