One of the longest rivers of the Eastern Seaboard of the United States, it rises in Otsego Lake, central New York state, and winds through the Appalachian Plateau in New York, Pennsylvania, and Maryland before flowing into the head of Chesapeake Bay at Havre de Grace, Maryland. About 444 miles long, the river and its tributaries (which include the Chemung, Lackawanna, West Branch of the Susquehanna, and Juniata rivers) drain an area of 27,570 square miles. Though the river itself never served as an important waterway because of rapids and other obstructions, its valley was significant as a land route to the Ohio River system and later as a focus of coal mining.
The Susquehanna River is one of the oldest existing rivers in the world, being dated as 320–340 Mya, older than the mountain ridges through which it flows. These ridges resulted from the Alleghenian orogeny uplift events when Africa (as part of Gondwana) slammed into the Northern part of EurAmerica).
The Susquehanna basin reaches its ultimate outflow in the Chesapeake Bay. It was well established in the flat tidelands of eastern North America during the Mesozoic era about 252 to 66 million years ago. This is the same period when the Hudson, Delaware and Potomac rivers were established.