Monongahela River

Fort Pitt Bridge over Monongahela River, Pittsburgh.

Monongahela River, 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 furnishes hydroelectric power to several cities. The Monongahela, made navigable by means of locks, is a major barge route, carrying coal, coke, iron, and steel.