Ohio River

Ohio River
The widest point on the Ohio River is just north of downtown Louisville, where it is one mile (1.6 km) wide. Indiana is on the right towards the flood gates, Kentucky on the left, towards the locks. The jetty on the left is the entrance to the Louisville and Portland Canal.
Ohio River basin
Location
Country	United States
States	Pennsylvania, Ohio, West Virginia, Kentucky, Indiana, Illinois
Cities	Pittsburgh, PA, East Liverpool, OH, Steubenville, OH, Wheeling, WV, Parkersburg, WV, Huntington, WV, Ashland, KY, Portsmouth, OH, Cincinnati, OH, Louisville, KY, Owensboro, KY, Evansville, IN, Henderson, KY, Mount Vernon, IN, Paducah, KY, Cairo, IL
Physical characteristics
Source	Allegheny River
• location	Allegany Township, Potter County, Pennsylvania
• coordinates	41°52′22″N 77°52′30″W / 41.87278°N 77.87500°W / 41.87278; -77.87500
• elevation	2,240 ft (680 m)
2nd source	Monongahela River
• location	Fairmont, West Virginia
• coordinates	39°27′53″N 80°09′13″W / 39.46472°N 80.15361°W / 39.46472; -80.15361
• elevation	880 ft (270 m)
Source confluence
• location	Pittsburgh, Pennsylvania
• coordinates	40°26′32″N 80°00′52″W / 40.44222°N 80.01444°W / 40.44222; -80.01444
• elevation	730 ft (220 m)
Mouth	Mississippi River
• location	at Cairo, Illinois / Ballard County, Kentucky
• coordinates	36°59′12″N 89°07′50″W / 36.98667°N 89.13056°W / 36.98667; -89.13056
• elevation	290 ft (88 m)
Length	981 mi (1,579 km)
Basin size	203,940 sq mi (528,200 km2)[7]
Discharge
• location	Cairo[1]
• average	(Period: 1951–1980)281,000 cu ft/s (8,000 m3/s)[1]
Discharge
• location	Olmsted
• average	(Period: 2013–2023)338,000 cu ft/s (9,600 m3/s)[2]
• minimum	40,300 cu ft/s (1,140 m3/s)(2016/10/14)[2]
• maximum	1,240,000 cu ft/s (35,000 m3/s)(2019/02/24)[2]
Discharge
• location	Metropolis
• average	(Period: 1928–2014)279,100 cu ft/s (7,900 m3/s)[4]
• minimum	15,000 cu ft/s (420 m3/s)(1930/07/20)[3][4]
• maximum	1,850,000 cu ft/s (52,000 m3/s)(1937/02/01)[3][4]
Discharge
• location	Louisville
• average	(Period: 1929–2020)120,800 cu ft/s (3,420 m3/s)[6]
• minimum	877 cu ft/s (24.8 m3/s)(2010/09/21)[6]
• maximum	1,110,000 cu ft/s (31,000 m3/s)(1937/01/27)[6]
Discharge
• location	Pittsburgh
• average	(Period: 1934–2023)34,020 cu ft/s (963 m3/s)[5]
• minimum	2,100 cu ft/s (59 m3/s)(1957/09/04)[5]
• maximum	574,000 cu ft/s (16,300 m3/s) (1936/03/18)[5]
Basin features
Progression	Mississippi River → Gulf of Mexico
Tributaries
• left	Little Kanawha River, Kanawha River, Guyandotte River, Big Sandy River, Little Sandy River, Licking River, Kentucky River, Salt River, Green River, Cumberland River, Tennessee River
• right	Beaver River, Little Muskingum River, Muskingum River, Little Hocking River, Hocking River, Shade River, Scioto River, Little Miami River, Great Miami River, Wabash River

The Ohio River is a 981-mile-long (1,579 km) river in the United States. It is located at the boundary of the Midwestern and Southern United States, flowing in a southwesterly direction from western Pennsylvania to its mouth on the Mississippi River at the southern tip of Illinois. It is the third largest river by discharge volume in the United States and the largest tributary by volume of the north-south flowing Mississippi River, which divides the eastern from western United States.^[8] It is also the sixth oldest river on the North American continent. The river flows through or along the border of six states, and its drainage basin includes parts of 14 states. Through its largest tributary, the Tennessee River, the basin includes several states of the southeastern U.S. It is the source of drinking water for five million people.^[9]

The river became a primary transportation route for pioneers during the westward expansion of the early U.S. The lower Ohio River just below Louisville was obstructed by rapids known as the Falls of the Ohio where the elevation falls 26 feet (7.9 m) in 2 miles (3.2 km) restricting larger commercial navigation, although in the 18th and early 19th century its three deepest channels could be traversed by a wide variety of craft then in use. In 1830, the Louisville and Portland Canal (now the McAlpine Locks and Dam) bypassed the rapids, allowing even larger commercial and modern navigation from the Forks of the Ohio at Pittsburgh to the Port of New Orleans at the mouth of the Mississippi on the Gulf of Mexico. Since the "canalization" of the river in 1929, the Ohio has not been a natural free-flowing river; today, it is divided into 21 discrete pools or reservoirs by 20 locks and dams for navigation and power generation.^[10]

The name "Ohio" comes from the Seneca, Ohi:yo', lit. "Good River".^[11] In his Notes on the State of Virginia published in 1781–82, Thomas Jefferson stated: "The Ohio is the most beautiful river on earth. Its current gentle, waters clear, and bosom smooth and unbroken by rocks and rapids, a single instance only excepted."^[12]

After the French and Indian War, Britain's trans-Appalachian Indian Reserve was divided by the river into colonial lands to the south and Native American lands to the north. In the late 18th century, the river became the southern boundary of the Northwest Territory. The river is sometimes considered as the western extension of the Mason–Dixon line that divided Pennsylvania from Maryland, and thus part of the border between free and slave territory, and between the Northern and Southern United States or Upper South. Where the river was narrow, it was crossed by thousands of slaves escaping to the North for freedom; many were helped by free blacks and whites of the Underground Railroad resistance movement.

The Ohio River is a climatic transition area, as its water runs along the periphery of the humid subtropical and humid continental climate areas. It is inhabited by fauna and flora of both climates. Today, the Ohio River is one of the most polluted rivers in the United States. In winter, it regularly freezes over at Pittsburgh but rarely farther south towards Cincinnati and Louisville. Further down the river in places like Paducah and Owensboro, Kentucky, closer to its confluence with the Mississippi, the Ohio is ice-free year-round.