The Allegheny River is located in the Northeastern United States and is a principal tributary of the Ohio River. The river rises in Pennsylvania and flows north into New York, and south into Pennsylvania again joining with the Monongahela River in the middle of Pittsburgh. Pittsburgh developed at this confluence. The Allegheny and the Monongahela confluence is the beginning of the Ohio River. The Allegheny’s largest tributaries are the Kiskiminetas, Clarion, and Conemaugh rivers and the Red Bank, Oil, and French creeks. Its tributaries reach to within 8 miles (13 km) of Lake Erie in southwestern New York.
The river is approximately 321 miles (517 km) long, and drains a rural dissected plateau of 11,580 square miles (30,000 km²) in the northern Allegheny Plateau, providing the farthest northeastern drainage in the watershed of the Mississippi River. The valley of the Allegheny River is one of the most productive areas of energy extraction in U.S. history, with extensive deposits of coal, petroleum, and natural gas.
In 1992, 86.6 miles (139.4 km) of the Allegheny River was designated a National Wild and Scenic River. This designation comprises three segments of the river located in Warren, Forest and Venango Counties. Seven islands in the river located between Kinzua Dam and Oil City, total 368 acres (1 km²), comprise the Allegheny Islands Wilderness, the smallest federally designated wilderness area in the United States. These designations have been made due to the significant ecological, scenic and recreational features of the river.
Much of the area through which the Allegheny River flows consists of hilly woodlands.
In its upper reaches the Allegheny is joined from the south by Potato Creek in McKean County, Pennsylvania and from the north by Olean Creek at Olean, New York. The Great Valley Creek and Little Valley Creek join the river from the north in Salamanca, New York before becoming the Allegheny Reservoir. After re-entering Pennsylvania, it is joined from the east by Kinzua Creek 10 miles (16 km) upstream of Warren; from the north by Conewango Creek at Warren; from the west by Brokenstraw Creek; from the north by Oil Creek at Oil City; from the west by French Creek at Franklin; from the east by the Clarion River in Parker, Pennsylvania, one of its principal tributaries, in eastern Clarion County; from the east by Crooked Creek southeast of Kittanning; and from the east by the Kiskiminetas River, another principal tributary, at Freeport. Buffalo Creek enters at Freeport, Bull Creek enters at Tarentum. There are numerous other creeks, runs, and streams that enter or join with the Allegheny River.
Credit: New World Encyclopedia