- Ohio River
a major river in the eastern central US. It begins at Pittsburgh, Pennsylvania, where the Allegheny River and Monongahela River come together, and flows 981 miles/1 578 kilometres past Cincinnati and into the Mississippi River at Cairo, Illinois. The Ohio was the main route to the West in the late 18th and early 19th centuries.
* * *Major river, eastern central U.S. Formed by the confluence of the Allegheny and Monongahela rivers, it flows northwest out of Pennsylvania, and west and southwest to form the state boundaries of Ohio–West Virginia, Ohio-Kentucky, Indiana-Kentucky, and Illinois-Kentucky.After a course of 975 mi (1,569 km), it empties into the Mississippi River at Cairo, Ill. It is navigable and has supported commerce since the earliest settlements. The river's strategic importance was recognized by the 1750s. After the French and Indian War, the English controlled the territory around the river.
* * *major river artery of the east-central United States. Formed by the confluence of the Allegheny (Allegheny River) and Monongahela (Monongahela River) rivers at Pittsburgh, it flows northwest out of Pennsylvania, then in a general southwesterly direction to join the Mississippi River at Cairo, Illinois (see photograph—>), after a course of 981 miles (1,579 km). It marks several state boundaries: the Ohio–West Virginia, Ohio–Kentucky, Indiana–Kentucky, and Illinois–Kentucky. The Ohio River contributes more water to the Mississippi than does any other tributary and drains an area of 203,900 square miles (528,100 square km). The river's valley is narrow, with an average width of less than 0.5 mile (0.8 km) between Pittsburgh and Wheeling (West Virginia), a little more than 1 mile (1.6 km) from Cincinnati (Ohio) to Louisville (Kentucky) and somewhat greater below Louisville.The Ohio is navigable, and, despite seasonal fluctuations that occasionally reach flood proportions, its fairly uniform flow has supported important commerce since settlement first began. Following destructive floods at Johnstown, Pennsylvania, in 1889 and Portsmouth, Ohio, in 1937, the federal government built a series of flood-control dams. While not developed for hydropower in Ohio, the river, kept at a navigable depth of 9 feet (3 metres), carries cargoes of coal, oil, steel, and manufactured articles. It has a total fall of only 429 feet (130 metres), the one major hazard to navigation being the Falls of the Ohio at Louisville, where locks control a descent of about 24 feet (7 metres) within a distance of 2.5 miles (4 km).The Ohio's tributaries include the Tennessee (Tennessee River), Cumberland (Cumberland River), Kanawha (Kanawha River), Big Sandy (Big Sandy River), Licking (Licking River), Kentucky (Kentucky River), and Green (Green River) rivers from the south and the Muskingum (Muskingum River), Miami (Miami River), Wabash (Wabash River), and Scioto (Scioto River) rivers from the north. Chief cities along the river, in addition to Pittsburgh, Cairo, Wheeling, and Louisville, are Steubenville, Marietta, Gallipolis, Portsmouth, and Cincinnati in Ohio; Madison, New Albany, Evansville, and Mount Vernon in Indiana; Parkersburg and Huntington in West Virginia; and Ashland, Covington, Owensboro, and Paducah in Kentucky.René-Robert Cavelier, Sieur de La Salle (La Salle, René-Robert Cavelier, sieur (lord) de), is said to have been the first European to see the Ohio, in 1669, and he descended it until obstructed by a waterfall (presumably the Falls at Louisville). In the 1750s the river's strategic importance (especially the fork at Pittsburgh) in the struggle between the French and the English for possession of the interior of the continent became fully recognized. By the treaty of 1763 ending the French and Indian Wars (French and Indian War), 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.
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