river, 981 mi (1,579 km) long, formed by the confluence of the Allegheny
rivers in SW Pa., at Pittsburgh; it flows northwest, then generally southwest to enter the Mississippi
River at Cairo, Ill. The Ohio's course follows a portion of the southern edge of the region covered by continental ice during the late Cenozoic era; glacial meltwater probably cut its original channel. The river is a major tributary of the Mississippi and supplies more water to it than does the Missouri
River. The Ohio River basin covers c.204,000 sq mi (528,400 sq km); the chief tributaries are the Tennessee
, and Kentucky
Sections in this article:
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.