Allegheny

River flowing through Pennsylvania and New York states, USA; length 523 km/325 mi. One of the main tributaries of the Ohio River, it rises in the Allegheny Plateau region of Potter County, Pennsylvania, and meets the Monongahela to form the Ohio near Pittsburgh.

Course It flows northwest from its source into New York, where it turns abruptly southwest, subsequently reentering Pennsylvania and passing Warren, Oil City, and Franklin before continuing southeast to pass Kittanning. It meets the Monongahela in what is considered one of the most beautiful river junctions in North America, often called the Golden Triangle.

History and current use Before the coming of railroads, the river was an important commercial channel. It is still used to transport bulk cargo, and some navigational locks and dams remain above Pittsburgh.