The '''Ohio River''' is the largest [[tributary]] of the [[Mississippi River]], and is approximately 981 miles long. The Ohio has an important tributary in the [[Tennessee River]], and drains much of the eastern United States west of the [[Appalachian Mountains]]. | The '''Ohio River''' is the largest [[tributary]] of the [[Mississippi River]], and is approximately 981 miles long. The Ohio has an important tributary in the [[Tennessee River]], and drains much of the eastern United States west of the [[Appalachian Mountains]]. |