Approximately one-fourth of its drainage comes from Illinois. The Wabash is one of the largest free flowing rivers east of the Mississippi River. It flows unimpeded for over 400 miles from the Huntington Dam in Indiana to its confluence with the Ohio. The Wabash does not have commercial navigation.
The Lower and Middle Wabash River has a total drainage of 33,000 square miles of which about two-thirds is agricultural.