Allegheny

Allegheny, river of Pennsylvania and New York. It rises in northern Pennsylvania, nearly 610 m (2,000 ft) above sea level, and merges with the Monongahela River at Pittsburgh, Pennsylvania, to form the Ohio River. Although the river flows through a hilly region, it is navigable by small boats for nearly 322 km (200 mi) above Pittsburgh. Unusually heavy flooding has necessitated the building of several reservoirs. The Allegheny is about 523 km (325 mi) long and drains an area of about 28,490 sq km (11,000 sq mi). Seven islands in the river form part of the Allegheny River Islands wilderness, a protected area within the Allegheny National Forest.