The Susquehanna River is a river in the northeastern United States, approximately 410 mi (715 km) long. The river forms of two main branches, with the North Branch, which rises in upstate New York often regarded as an extension of the main branch. The shorter West Branch, which rises in western Pennsylvania, is sometimes regarded as the principal tributary, joining the North Branch near Sunbury in central Pennsylvania. The river drains a large watershed within the Allegheny Plateau of the Appalachian Mountains, cutting through water gaps in the lateral mountain ridges is a broad zigzag course to flow across the rural heartland of southeastern Pennsylvania, emptying in the north end of the Chesapeake Bay.
Rising near Cooperstown, New York, the north branch of the river river runs east southeast through dairy country, receiving the Unadilla River at Sidney and the Chenango in downtown Binghamton. At Sayre in northern Pennsylvania, just across the New York state line, it receives the Chemung from the northwest and makes a right angle curve between Sayre and Towanda to cut through The Endless Mountains in the Allegheny Plateau. It receives the Lackawanna River southwest of Scranton and turns sharply to the southwest, flowing through the former industrial heartland in the mountain ridges of northeastern Pennsylvania, past Wilkes-Barre, Berwick, Bloomsburg, and Danville. It receives the smaller West Branch from the northwest at Sunbury.
Harrisburg, with the state capitol dome from across the Susquehanna River
Downstream from the confluence of its branches it flows south past Selinsgrove and cutting through a water gap at the western end of Mahantango Mountain. It receives the Juniata River from the northwest at Duncannon, then passes through its last water gap, through Blue Mountain, just northwest of Harrisburg. It passes downtown Harrisburg (where it is nearly a mile wide), the largest city on the lower river, and flows southeast across rural south central Pennsylvania, receiving Swatara Creek from the northeast. It crosses into northern Maryland approximately 30 mi northeast of Baltimore and enters the northern end of the Chesapeake Bay at Havre de Grace.
Geologically, the river is older than the mountains through which it turns. The Chesapeake Bay is post-Pleistocene remnant of the lower river valley that was flooded by the rising waters after the ice age.
The river has played an enormous role throughout the history of the United States. In the 17th century it was inhabited largely by the Lenape, forming roughly the western boundary of their inhabited territory, known as Lenapehoking. In the 18th century, William Penn, the founder of the Pennsylvania Colony, negotiated with the Lenape to allow white settlement in the colony between the Delaware River and Susquehanna. The name of the river comes from an Algonquian word for "muddy water."
In the late colonial times the river became an increasingly important transportation corridor with the discovery of anthracite coal in its upper reaches in the mountains. In 1792, the Union Canal was proposed linking the Susquehanna and the Delaware along Swatara Creek and Tulpehocken Creek. In the 18th century. In the 19th century the river became the scene of the growth of industrial centers.
In 1972 the remnants of Hurricane Agnes stalled over the New York-Pennsylvania Border, dropping as much as 20 inches of rain on the hilly lands. Much of that precipitation was received into the Susquehanna from its western tributaries and the valley suffered disastrous flooding. Wilkes-Barre, Pennsylvania, was among the hardest hit communities. The Chesapeake Bay received so much fresh water that it killed off much of the marine life.
In 1979 the river was the scene of the most serious nuclear power accident in U.S. history at Three Mile Island southeast of Harrisburg. The river suffered the dumping of more than 40,000 gallons (150 m³) of radioactive fuel during the meltdown.