ALLEGHENY RIVER, a river of Pennsylvania and New York and the principal tributary of the Ohio river, whose source is the confluence of the Allegheny and the Monongahela at Pitts burgh. The Allegheny rises in the high, hilly plateau region of Potter County, Pa., at an elevation of about 2,25oft. above sea level. From its source it flows in a general north-westerly direc tion about 8om., crossing into New York, to a point um. N. of the State line. Here it turns abruptly south-west and continues in this direction for to the central part of Venango county, Pennsylvania. It then turns to the south-east and again south west to its confluence with the Monongahela at Pittsburgh. Its total length is about 31 om. and its drainage basin 1 1 ,40o sq. miles. The topographical character of its drainage basin ranges from the steep hills and broken country of the eastern slope to the comparatively level marshy western slope. The chief tribu taries of the Allegheny are Conewango creek (which flows from the lake region of Chautauqua county, N.Y.), French creek, and Clarion and Kiskiininetas rivers. The Allegheny once served as an important highway for keel-boat navigation and later for trans porting the petroleum and coal produced along its banks, but this was only before the beginning of railway competition. The canal ized portion of the river, extending from Pittsburgh to Natrona (24m.) and seven feet in depth, has an annual traffic valued at about $12,000,000.