At 981 miles, the Ohio River is the longest river in Pennsylvania, running from Pittsburgh, Pennsylvania, to Cairo, Illinois. It is followed by the Susquehanna River at 464 miles, the Allegheny River at 325 miles, and the Delaware River at 301 miles.
The Susquehanna River, originating in New York and eventually draining into the Chesapeake Bay in Maryland, runs the entire length of Pennsylvania, flowing primarily in the eastern and central part of the state, including through the state capital of Harrisburg. The Allegheny River runs through a major portion of western Pennsylvania and drains into the Ohio River at Pittsburgh. The Delaware River forms Pennsylvania’s eastern border with both New York and New Jersey.