About 981 miles · 6 states · source Pittsburgh, PA · mouth Cairo, IL
Ohio River map
The Ohio flows about 981 miles from Pittsburgh, where the Allegheny and Monongahela meet, to the Mississippi at Cairo, Illinois. It forms the entire northern border of Kentucky and West Virginia's western edge.
Where the Ohio is
The Ohio starts at the Point in Pittsburgh, Pennsylvania, at the confluence of the Allegheny and Monongahela. It flows northwest for a short stretch, then southwest for about 981 miles to Cairo, Illinois, where it enters the Mississippi. At Cairo it actually carries more water than the Mississippi does, making it the largest tributary by volume in the whole system.
States along the river
- Pennsylvania — the first 40 miles, Pittsburgh to the Ohio–West Virginia line.
- Ohio — the state's entire southern and southeastern border, with Cincinnati.
- West Virginia — the western border from the northern panhandle down to Huntington.
- Kentucky — the entire northern border, about 660 miles, with Louisville, Covington, Owensboro and Paducah.
- Indiana — the entire southern border, with Evansville.
- Illinois — the southeastern border to Cairo.
Kentucky owns the river bed. When Virginia ceded its western lands in 1784, the boundary was set at the low-water mark on the northern bank, so the border with Ohio, Indiana and Illinois runs along the far shore rather than mid-channel.
Key measurements
- Length: about 981 miles.
- Basin: about 204,000 square miles across 14 states.
- Tributaries: the Kanawha, Kentucky, Green, Wabash (which forms most of the Indiana–Illinois line), Cumberland and Tennessee. The Tennessee and Cumberland join within 12 miles of each other near Paducah.
- Navigation: 20 locks and dams give a 9-ft channel the full length; the Falls of the Ohio at Louisville, the only natural obstacle, are bypassed by the McAlpine Locks.
Cities on the river
Pittsburgh at the head, then Wheeling, Huntington, Cincinnati (with Covington and Newport across the water in Kentucky), Louisville, Evansville and Paducah. Louisville is the largest; it exists because boats had to unload above the falls.
How the river shaped the map
The Northwest Ordinance of 1787 made the Ohio the southern edge of the Northwest Territory and banned slavery north of it, so the river became the line between free and slave states from Pennsylvania to the Mississippi. That is why Ohio, Indiana and Illinois all end at the water while Kentucky's northern edge is a single continuous curve. The river also gives West Virginia its irregular western border. West of Pittsburgh the Appalachian plateau drops to the river valley; downstream of Louisville the country flattens into the Midwest.
Related maps
- Mississippi River — where the Ohio ends.
- Appalachian Mountains — the source region.
- Mason–Dixon Line — the other free–slave boundary line.
- Longest US rivers · All geography maps.