Navigable branches of the Ohio River, from 1897, from the US Army Corps of Engineers.
The Ohio River is the largest tributary of the Mississippi River, by volume. It flows for 981 miles from Pittsburgh to where the river empties into the Mississippi at Cairo, Illinois.
The Ohio River drains a basin of 204,000 square miles. The Allegheny and Monongahela rivers meet at what is now Pittsburgh, to form the Ohio. Other tributaries include the Green, Cumberland, Tennessee, Beaver, Muskingum, Scioto, Miami, and Wabash rivers.
Before engineers built locks, and dredged shallow reaches, the river's average speed was five miles per hour.
The Falls of the Ohio, at present day Louisville, Kentucky, was the only navigational obstacle on the Ohio, until it was circumvented by a canal.