river formed by the confluence of the Tygart and West Fork rivers in Marion county, West Virginia, U.S. It flows 128 miles (206 km) in a northerly direction past Morgantown into Pennsylvania, past Brownsville and Charleroi, joining the Allegheny River at Pittsburgh to become a major headwater of the Ohio River. In its upper reaches the river has a swift current and furnishes hydroelectric power to several cities. The Monongahela, made navigable by means of locks for 106 miles (170 km), is a major barge route, carrying coal, coke, iron, and steel.