ALLEGHANY River, in Pennsylvania, rises on the western side of the Alleghany mountains, and after running about 200 miles in a south-west direction, meets the Monongahela at Pittsburg, and both united form the Ohio. The lands on each side of this river, for 150 miles above Pittsburg, consist of white oak and chestnut ridges, and in many places of poor pitch pines, interspersed with tracts of good land, and low meadows. This river, and the Ohio likewise, from its head waters until it enters the Mississippi, are known and called by the name of Alleghany River, by the Seneca, and other tribes of the Six Nations, who once inhabited it.