River, central New York, Pennsylvania, and Maryland, U.S. One of the longest rivers in the eastern U.S., it is about 444 mi (715 km) long.
It rises in Otsego Lake, central New York, and winds through the Appalachian Mountains before flowing into northern Chesapeake Bay . Though it was never an important waterway because of obstructions, including rapids, its valley was at one time a significant land route to the Ohio River system and was later a coal-mining region.