Main Page | See live article | Alphabetical index The Allegheny River (historically, especially in New York state, also spelled Allegany River) is a river in the eastern United States of America. It rises in Potter County, Pennsylvania, flows northwestward into New York State (where it just misses the county named for it, Allegany County; its entire course in New York State is within the adjacent county, Cattaraugus County), then turns southwestward back into Pennsylvania, joining the Monongahela River at Pittsburgh, Pennsylvania. The combined river is known as the Ohio River, which ultimately joins the Mississippi to flow to the Gulf of Mexico. The Allegheny is one of the easternmost rivers of the Mississippi River system. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.