The Ohio River is a major river artery of the east-central United States.
The length of the Ohio River is approximately 1,579 kilometers (981 miles). It is the 10th longest river in the United States.
The Ohio River is formed by the confluence of the Allegheny and Monongahela rivers at Point State Park in Pittsburgh, Pennsylvania. From there, it flows northwest through Allegheny and Beaver counties, before making an abrupt turn to the south-southwest at the West Virginia–Ohio–Pennsylvania triple-state line. From there, it forms the border between West Virginia and Ohio, upstream of Wheeling, West Virginia.
The river then follows a roughly southwest and then west-northwest course until Cincinnati, before bending to a west-southwest course for most of its length. The course forms the northern borders of West Virginia and Kentucky; and the southern borders of Ohio, Indiana and Illinois, until it joins the Mississippi River near the city of Cairo, Illinois.
The Ohio River is the largest tributary, by volume, of the Mississippi River in the United States.
At the confluence, the Ohio is considerably bigger than the Mississippi (Ohio at Cairo: 281,500 cu ft/s (7,960 m3/s); Mississippi at Thebes: 208,200 cu ft/s (5,897 m3/s)) and, thus, is hydrologically the main stream of the whole river system.
The Ohio River is a naturally shallow river that was artificially deepened by a series of dams. The natural depth of the river varied from about 0.9 to 6 meters (3 to 20 feet). The dams raise the water level and have turned the river largely into a series of reservoirs, eliminating shallow stretches and allowing for commercial navigation. From its origin to Cincinnati, the average depth is approximately 5 meters (15 feet).
The first dam and lock was built on the Ohio River in 1885, with an entire system of 46 locks and dams built until 1929. In the early 1950s the Army Corps of Engineers began replacing the old structures with 20 modern locks and dams with higher lifts and much longer lock chambers.
The dams have greatly changed the flow of the river, creating a series of very slow moving pools rather than a free flowing river.
The Ohio’s tributaries include the Tennessee, Cumberland, Kanawha, Big Sandy, Licking, Kentucky, and Green rivers from the south and the Muskingum, Miami, Wabash, and Scioto rivers from the north.
Cities along the river include: Pittsburgh, East Liverpool, Wheeling, Parkersburg, Huntington, Ashland, Cincinnati, Louisville, Owensboro, Evansville, Henderson, Paducah, Cairo.
The Ohio’s drainage basin covers 490,600 square kilometers (189,422 square miles), encompassing the easternmost regions of the Mississippi Basin.
The Ohio’s drainage basin includes parts of 15 states: New York, Pennsylvania, Maryland, West Virginia, Kentucky, Tennessee, Virginia, North Carolina, Ohio, Indiana, Illinois, Georgia, Alabama, Mississippi and South Carolina.
The Ohio River is a climatic transition area as its water runs along the periphery of the humid subtropical climate and humid continental climate thereby being inhabited by fauna and flora of both climates.
The Ohio River Islands National Wildlife Refuge is a National Wildlife Refuge in non-contiguous sites consisting of islands along 631 kilometers (392 miles) of the Ohio River, primarily in the U.S. state of West Virginia. Over 25 different species of mammals live on the refuge land, ranging from the white-tailed deer, raccoons, muskrats, and mink to the cottontail rabbit and red fox. In the depths and shallows of the Ohio River, well over 100 different species of fish exist.
The Falls of the Ohio National Wildlife Conservation Area is a national, bi-state area on the Ohio River near Louisville, Kentucky in the United States, administered by the U.S. Army Corps of Engineers. Federal status was awarded in 1981. The falls were designated a National Natural Landmark in 1966.
Pre-Columbian inhabitants of eastern North America considered the Ohio part of a single river continuing on through the lower Mississippi. The river’s name comes from the Seneca (Iroquoian) Ohiːyo’, a proper name derived from ohiːyoːh, meaning “good river”.
The first known European explorer to travel the river was French explorer René-Robert Cavelier, Sieur de La Salle, in 1669.
In 1749, Great Britain established the Ohio Company to settle and trade in the area. Exploration of the territory and trade with the Indians in the region near the Forks by British colonials from
Pennsylvania and Virginia – both of which claimed the territory – led to conflict with the French.
By the treaty of 1763 ending the French and Indian Wars, the English finally gained undisputed control of the territory along its banks. When (by an ordinance of 1787) the area was opened to settlement, most of the settlers entered the region down the headwaters of the Ohio.
From a geological standpoint, the Ohio River is young. The river formed on a piecemeal basis beginning between 2.5 and 3 million years ago. The earliest ice ages occurred at this time and dammed portions of north-flowing rivers.
The Ohio River is the source of drinking water for more than three million people.