Alleghany River rises in Potter county, N. Pennsylvania, flows circuitously westward through New York, returns to Pennsylvania, and after a southerly course unites at Pittsburgh with the Monongahela river to form the Ohio. It flows through a hilly country, abounding in pine forests and coal. The river is navigable for small steamboats to Olean, N. Y., 240 m. from its mouth and about 45 m. from its source, and to Waterford, Pa., on French creek, its principal tributary, 14 m. from Lake Erie. Its chief tributary from the east is the Conemaugh. The principal towns along its course are Warren, Kittanning, Franklin, and Oil City. The Alleghany separates Pittsburgh from Allegheny City.