The Chemung River (shuh-MUHNG) is a tributary of the Susquehanna River, approximately 45 mi (72 km) long, in south central New York an northern Pennsylvania in the United States. It drains a mountainous region of the northern Allegheny Plateau in the Southern Tier of New York. The valley of the river has long been an important manufacturing center in the region but has suffered a decline in the late 20th century.