The Ohio River system is a major tributary of the Mississippi River and drains a significant portion of the Appalachian Mountains, including parts of Pennsylvania, Ohio, Kentucky, West Virginia, Indiana, and Illinois.

The Ohio River is a major river system that drains much of the Appalachian region. It flows through several states, including Pennsylvania, Ohio, Kentucky, West Virginia, Indiana, and Illinois. The Ohio River is an important transportation route and is also a popular destination for fishing and boating.