Ohio River

At a glance

Before Ohio

The Ohio River begins at Pittsburgh, where the Allegheny and Monongahela meet, and flows southwest 981 miles to the Mississippi at Cairo, Illinois, draining a basin of 203,940 square miles across parts of 14 states (ORSANCO, 2026). Ohio meets it 40.2 miles below Pittsburgh, at the Pennsylvania line, and follows it to mile 491.3, just below the mouth of the Great Miami, where Indiana takes over the north bank (ORSANCO, 2026). That gives Ohio 451 miles of riverfront, second among the commission's member states only to Kentucky's 664 (ORSANCO basin data). The state transportation department's Ohio River Scenic Byway counts 14 counties and 452 miles (Ohio DOT story map).

The state is named for the river, and the river's name is Native. Ohio University's College of Arts and Sciences says "Ohio" comes from a Seneca (Iroquois) word meaning "good" or "great river" (Ohio University). A state historical marker at Middleport gives the Iroquois forms as "Oyo" or "Ohio," which the French translated as La Belle Riviere, the Beautiful River (marker 16-53). Jacques Marquette and Louis Jolliet saw its mouth on the Mississippi in June 1673, as the first-Europeans long read tells (Marquette, in Kellogg, 1917).

In geological terms the river is new. Before the Ice Age, western and southern Ohio drained through the Teays River, a stream comparable in size to the modern Ohio, which followed the present Ohio River to Wheelersburg before turning north (ODNR GeoFacts No. 10). The earliest glacier dammed the Teays and backed up Lake Tight across about 7,000 square miles of southern Ohio, West Virginia and Kentucky (ODNR GeoFacts No. 10). When the lake spilled over old drainage divides it cut new channels below the Teays' bed, the stage geologists call Deep Stage, and the state geological survey calls that the beginning of the modern Ohio River drainage system (ODNR GeoFacts No. 10). Near Wheelersburg in Scioto County an abandoned stretch of the old Teays valley still sits about 150 feet above the modern river channel beside it (ODNR GeoFacts No. 10). The full story is in the site's Ice Age glaciers long read.

The border

The river became a line on paper before Ohio existed. The Northwest Ordinance of July 13, 1787, which organized the territory "northwest of the river Ohio," barred slavery there in its sixth article (Avalon Project). Two years earlier, on September 30, 1785, the surveyor Thomas Hutchins had begun the first federal land survey from a stake on the north bank of the river near modern East Liverpool (NHL nomination). The 1795 Treaty of Greenville, signed after the battle described in the site's Fallen Timbers long read, ran its boundary southwest to the Ohio near the mouth of the Kentucky River (Kappler, 1795); the road to statehood long read follows that story.

Exactly where in the river the line runs took the Supreme Court to settle. Ohio sued Kentucky in 1966, and on January 21, 1980 the Court held that "the boundary between Ohio and Kentucky is the low-water mark on the northerly side of the Ohio River as it existed in 1792," the year Kentucky became a state (Ohio v. Kentucky, 444 U.S. 335). Kentucky had argued for the river's current low-water mark, which the Court described as "a still more northerly mark due to the later damming of the river and the consequent rise of its waters" (Ohio v. Kentucky). Justice Harry Blackmun wrote for the majority, adopting Special Master Robert Van Pelt's report; Justice Lewis Powell, joined by Justices White and Rehnquist, dissented, warning that the ruling created a "largely unidentifiable border" (Ohio v. Kentucky). The Court read the 1784 cession as making the river's northerly edge, not its middle, the line, so the water opposite Kentucky lies in Kentucky (Ohio v. Kentucky).

A highway west

Before steam, the river carried three kinds of boats, as J. H. B. Latrobe described them in 1871 from the stories of the first steamboat voyage he had grown up hearing (Latrobe, 1871). Long, slender keelboats could be poled upstream; a keelboat covered with a low house was called a barge (Latrobe, 1871). The flatboat, or "broad horn," was, in his words, "an unwieldly box," floated downstream only and broken up for its lumber at the end of the trip (Latrobe, 1871).

The first Ohio towns were founded from such boats. The Ohio Company pioneers left Sumrill's Ferry on the Youghiogheny on April 2, 1788 in a 45-foot covered galley with a flatboat and three canoes, and landed at the mouth of the Muskingum on April 7 to found Marietta (Hildreth, Pioneer History), as told in the site's Marietta long read. About 500 French immigrants reached Gallipolis by flatboat from Pittsburgh on October 17, 1790 (marker 14-27), and New England settlers came by flatboat to "Belle-Prairie," now Belpre, in 1789 (marker 17-84).

The steamboat changed the river's direction of business. Nicholas Roosevelt built the New Orleans at Pittsburgh for about $38,000 and set off in the latter part of September 1811, with his wife aboard against the advice of their Pittsburgh friends (Latrobe, 1871). On the second day the boat "rounded to opposite Cincinnati, and cast anchor in the stream," and onlookers told the Roosevelts the boat might go down the river but never up it (Latrobe, 1871). The boat reached Louisville at midnight on October 1, 1811, rode out the earthquakes that shook the Mississippi valley that winter, and arrived at Natchez at the close of the first week of January 1812 (Latrobe, 1871).

The Ohio and Erie Canal, built between 1825 and 1832, ran 308 miles from Lake Erie at Cleveland to the Ohio River at Portsmouth (marker 30-25). On the west side, canal boats were running from Hartwell's Basin near Cincinnati to Middletown by November 28, 1827, the first link in what became the Miami and Erie Canal, joining Toledo and Cincinnati by water in 1845 (marker 1-9). In Cincinnati that canal divided downtown from the German district that took its nickname from it, as the Over-the-Rhine long read explains. Portsmouth, platted in 1803 after flooding drove settlers off the low ground at Alexandria across the Scioto, was Scioto County's business center by 1814 (marker 8-73).

Slavery and freedom on the river

Before the Civil War the river divided slave states from a free one. On the north bank the Northwest Ordinance said there "shall be neither slavery nor involuntary servitude," although the same article let people "from whom labor or service is lawfully claimed" be returned (Avalon Project).

At Ripley, in Brown County, the Presbyterian minister John Rankin and his family sheltered people who had crossed from Mason County, Kentucky, at their brick house on a hill about 400 feet above the riverbank, from the 1820s until the end of the Civil War (NHL nomination). The African American ironworker John P. Parker crossed into Kentucky for some fifteen years to bring people out, and named 315 of them in a diary he later burned (NHL nomination); the National Park Service credits him and Rankin together with aiding as many as 1,000 (NPS, 2018). The Rankin family said John Rankin told Lyman Beecher and the Stowes, during a church synod at Ripley in 1838, of a woman who had crossed the frozen river with her child, a story tradition ties to Eliza in Uncle Tom's Cabin (NHL nomination). The Rankin House long read weighs that account; the Stowe House long read covers the Cincinnati side.

Cincinnati's bridge fight carried the same tension. Ohio lawmakers, pressed by ferry and steamboat interests and by fears that a bridge would help enslaved people escape, held back the Covington and Cincinnati Bridge Company's plans for years, as the site's Roebling Bridge long read recounts (Cincinnati Enquirer, 2011, archived). The bridge opened to all traffic on January 1, 1867 (roeblingbridge.org).

Building the locks and dams

The federal government has worked on the channel for two centuries. Congress first acted to improve navigation in 1824 and began canalizing the river with locks and dams in 1878 (marker 16-53). The first, Davis Island Dam near Pittsburgh, was finished in 1885; by 1929 a nine-foot pool ran the length of the river down to Lock and Dam 53 at Grand Chain, Illinois (marker 6-41). Lock and Dam 10 at Steubenville, completed in 1915 with a brick powerhouse and two lockkeeper houses, was replaced by Pike Island and its buildings demolished in 1975; steps, a 600-foot ramp and part of the lock wall survive at the Steubenville marina (marker 6-41).

The modern river is a staircase of high-lift dams, each holding a pool named for the dam below it (ORSANCO, 2026). Nine of them stand on Ohio's stretch, and the Corps' Ohio fact sheet lists all nine as the state's locks (Army Corps, 2023). ORSANCO's table, drawn from the Corps' Ohio River Division, dates each to the year its pool was raised and gives its normal pool in feet above sea level:

New Cumberland (mile 54.4, 1959, pool 664.5 feet), Pike Island (mile 84.2, 1963, 644 feet), Hannibal (mile 126.4, 1972, 623 feet), Willow Island (mile 161.7, 1972, 602 feet), Belleville (mile 203.9, 1965, 582 feet), Racine (mile 237.5, 1967, 560 feet), Robert C. Byrd (mile 279.2, 1937, 538 feet), Greenup (mile 341.0, 1962, 515 feet) and Meldahl (mile 436.2, 1964, 485 feet) (ORSANCO). The difference between a dam's pool and the next one downstream, the lift a tow rides through each lock, runs from 20 to 23 feet, except 30 feet at Greenup and at Meldahl.

The last two wicket dams, Locks and Dams 52 and 53, were made obsolete when Olmsted Locks and Dam opened in August 2018, leaving the river with 19 high-lift dams that keep a minimum depth of nine feet (ORSANCO, 2026). A Belpre marker describes the town as sitting on a 42-mile Ohio River "lake" worked by tows of barges up to 1,200 feet long (marker 17-84).

ORSANCO's river facts put the river's cargo at more than 184 million tons a year (ORSANCO), while its 2026 assessment says barges carry "in excess of 280 million tons" a year, mostly coal, oil and petroleum (ORSANCO, 2026). For Ohio alone, the Corps' navigation planning center in Huntington counted 32.2 million tons on the Ohio River in 2023, worth an estimated $7.72 billion, second in the state only to Lake Erie's 35.8 million tons (Army Corps, 2023).

Stories

The 1937 flood

The Ohio has always flooded. The U.S. Geological Survey's 1937 flood report notes a Cincinnati flood in 1772 that reached between 75 and 76 feet (USGS Water-Supply Paper 838, 1938). The National Weather Service lists the 1884 crest at Cincinnati at 71.1 feet on February 14 and the 1913 crest at 69.9 feet on April 1 (NWS gauge CCNO1). At Marietta, where the Muskingum joins the river, the record is still the 58.3 feet of March 29, 1913 (NWS gauge MTAO1).

January 1937 was worse. Over the storm period a mean of 12.85 inches of precipitation fell on the Ohio River basin, and 8.9 inches of it ran off as flood water (USGS WSP 838). The National Weather Service gives the Cincinnati crest as 80 feet on January 26, 1937, still the record and 28 feet above today's 52-foot flood stage (NWS gauge CCNO1). The river stood above flood stage along its whole length, about 1,000 miles from Pittsburgh to Cairo, from January 22 to 27, and set records for about 700 miles from Point Pleasant to Cairo; "loss of life was considerable," and more than 500,000 people were reported driven from their homes (USGS WSP 838). Cincinnati was short of drinking water; Pomeroy "became a ghost city," its stores, homes and schools evacuated (USGS WSP 838). The Roebling Suspension Bridge was the only highway crossing left open from Steubenville to Cairo (roeblingbridge.org), and Union Terminal's tracks and platforms stayed dry, as the Union Terminal long read describes (Cincinnati Museum Center, archived).

The wall at Portsmouth

Portsmouth went into the flood behind a 60-foot concrete wall (USGS WSP 838). Sandbagging on top of it began January 19; on January 20, with two feet of bags on the crest, residents began evacuating so the floodgates could be opened, to prevent heavy damage from water pouring over the wall (USGS WSP 838). On January 22 the Ohio and Scioto overwhelmed the city. The wall was overtopped by 14 feet of water (USGS WSP 838). The river crested at Portsmouth at 74.23 feet on January 27, 1937 (NWS gauge PORO1). A state marker says the three-mile levee, first built in 1908, failed in the flood and was later improved (marker 8-73); the city says the Army Corps of Engineers built a new floodwall after 1937 (City of Portsmouth).

In 1993 the city began painting the new wall. Robert Dafford of Lafayette, Louisiana, has been the artist for the whole project, which covers a 20-foot-high section of floodwall running 2,090 feet along Front Street in sixty consecutive panels (City of Portsmouth).

The Silver Bridge

At about 5 p.m. on December 15, 1967, the U.S. 35 bridge between Point Pleasant, West Virginia, and Kanauga, Ohio, collapsed into the river (NTSB, 1970). The National Transportation Safety Board counted 46 dead and nine injured; 31 of the 37 vehicles on the bridge fell with it, 24 into the river and seven on the Ohio shore (NTSB, 1970).

The bridge, built in 1928 for $1.2 million, hung from heat-treated eyebar chains rather than wire cables, and was called the Silver Bridge because it was the first in the world painted with aluminum paint, according to a state marker at the Kanauga rest area, which lists 22 of the dead as Ohioans (marker 8-27). The Safety Board found that the collapse began with a cleavage fracture in the eye of eyebar 330, in the north chain of the Ohio side span, caused by a flaw that grew over the bridge's 40-year life through "the joint action of stress corrosion and corrosion fatigue" (NTSB, 1970). The flaw, it added, could not have been found "by any inspection method known in the state of the art today without disassembly of the eyebar joint" (NTSB, 1970). West Virginia closed the sister St. Marys Bridge as a precaution during the investigation (NTSB, 1970), and the replacement Silver Memorial Bridge was dedicated in 1969 (marker 8-27).

The Brent Spence and its companion

At Cincinnati, Interstates 71 and 75 cross on the Brent Spence Bridge, which has carried traffic since 1963 (Kentucky governor's office, 2026). It was built to carry about 80,000 vehicles a day; by 2022 the two states said its daily load had reached 160,000 (Kentucky governor's office, 2022). In 1985 its emergency shoulders were removed to fit a fourth lane each way (Kentucky governor's office, 2026). In December 2022 Ohio and Kentucky announced federal grants of more than $1.6 billion for the project (Kentucky governor's office, 2022).

Governors Mike DeWine and Andy Beshear broke ground on May 8, 2026 on a $4.05 billion phase that adds a cable-stayed companion bridge for interstate traffic and leaves the old span for local traffic, with its shoulders restored and new paths for walkers and cyclists (Kentucky governor's office, 2026). The companion bridge is expected to open in 2031, with approach work substantially complete by 2033 (Kentucky governor's office, 2026). Each state pays for its own highway work, and the two share the cost of the new bridge (Kentucky governor's office, 2026).

The river since

A Belpre marker says that by the mid-1900s industry had replaced farming there and the town had become a center of polymer production (marker 17-84). ORSANCO counts about 45 power plants along the river, providing more than 5 percent of the nation's generating capacity (ORSANCO, 2026). Among them is the Gen. James M. Gavin plant at Cheshire in Gallia County, which the Associated Press described in 2022 as "one of the largest coal-fired electricity plants in the U.S." (AP via KSAT, 2022). That November the U.S. Environmental Protection Agency ordered the plant to stop putting coal ash into an unlined storage pond and to speed cleanup, the AP reported (AP via KSAT, 2022). In 2024 Gavin was Ohio's third-largest plant by generation, at 10.3 million megawatt-hours, behind a gas plant and a nuclear plant (EIA, 2025).

Most river towns are losing people. The Census Bureau's July 2024 estimates for river towns are these (Census Bureau, 2025):

• Cincinnati: 314,915
• Steubenville: 18,029
• Portsmouth: 17,489
• Marietta: 13,039
• Ironton: 10,147
• East Liverpool: 9,651
• Belpre: 6,588
• Martins Ferry: 6,050
• Bellaire: 3,745
• Gallipolis: 3,282
• New Richmond: 2,795
• Manchester: 1,858
• Ripley: 1,591
• Pomeroy: 1,505

Of these, only Cincinnati, Ripley, New Richmond and Manchester grew from their April 2020 counts (Census Bureau, 2025).

The river is also a place to play. The Ohio River Way, listed in ORSANCO's recreation pages, aims to connect people with "opportunities for adventure on and along the Ohio River" from Portsmouth, Ohio, to West Point, Kentucky (ORSANCO). Gallipolis's marker points to water sports, fishing and boating (marker 14-27). Swimmers are asked to be careful. ORSANCO says E. coli and other bacteria are present all year and that "if there has been significant rainfall in the past 48–72 hours, wait before swimming or wading," because combined sewer overflows flush contaminants into the river (ORSANCO). Flood forecasts come from the National Weather Service's Ohio River Forecast Center in Wilmington (NWS).

The water

The Ohio is a drinking-water source for about five million people through 32 utilities (ORSANCO, 2026). Its interstate watchdog, the Ohio River Valley Water Sanitation Commission, was established June 30, 1948 "to control and abate pollution in the Ohio River Basin" (ORSANCO). Governors of eight states signed its compact, and Congress approved it (ORSANCO, 2026).

The commission's 2026 biennial assessment, covering 2020 to 2024, found the entire river fully supporting aquatic life and public water supply (ORSANCO, 2026). It rated the whole river only partially supporting for fish consumption because of PCBs and dioxins, and listed 626.7 miles as impaired for contact recreation, including 235.3 of Ohio's 276.9 miles across from West Virginia and 69.3 of its 174.2 miles across from Kentucky (ORSANCO, 2026). The trend in fish is improving. Its biologists found that PCB levels in channel catfish fell from 1989 to 2021, most steeply before 2004, and that "Do Not Eat" records for PCBs had almost disappeared from modern collections (ORSANCO, 2026).

The largest algal bloom on record came in 2015. On August 19 of that year ORSANCO received a report of a paint-like green material covering 100 by 200 feet at Pike Island Locks and Dam (ORSANCO, 2021). It was the cyanobacterium Microcystis aeruginosa, and it produced microcystin in the river as high as 3,000 micrograms per liter (ORSANCO, 2021). Within a month the bloom stretched from Pike Island to Cannelton Locks and Dam, river miles 84.2 to 720.7, and Ohio, West Virginia, Kentucky and Indiana kept recreation advisories in place for two months (ORSANCO, 2021). The largest earlier bloom, in 2008, had covered about 30 miles for 10 days; another, in September 2019, was concentrated in the Greenup, Meldahl, Markland and McAlpine pools (ORSANCO, 2021).

The February 2023 train derailment at East Palestine tested the system's spill monitoring. Low levels of butyl acrylate were believed to have seeped into the river through Little Beaver Creek, Spectrum News reported (Spectrum News, 2023); the creek enters the river at mile 39.5, just above the Ohio line (ORSANCO, 2026). The highest reading in three weeks of testing was 12 parts per billion, in Little Beaver Creek itself; ORSANCO's executive director, Richard Harrison, said concern for butyl acrylate begins at 560 parts per billion and that near-flood water levels had diluted the chemicals (Spectrum News, 2023). Greater Cincinnati Water Works, which draws about 90 percent of its supply from the river, closed its intake at 2 a.m. on Sunday, February 19, "out of an abundance of caution," and reopened it the next day after finding "no detectable concentrations of chemicals related to the train derailment" (Spectrum News, 2023). A different compound, 2-ethyl-1-hexanol, turned up in a river sample, and the utility said it was not certain it came from the derailment; the Northern Kentucky Water District also closed and reopened its intakes (WCPO).

ORSANCO counts 160 species of fish (ORSANCO), or "over 140" in its 2026 report (ORSANCO, 2026). The U.S. Fish and Wildlife Service's Ohio River Islands National Wildlife Refuge, established in 1990 along 362 miles of the upper river, protects islands whose deep and shallow water are "major fish and mussel production areas" and emphasizes "endangered freshwater mussels" among its wildlife (USFWS).

Sources

• ORSANCO: 305(b) assessment, 2026, river facts, basin population, navigational dams, about, HAB plan, 2021, swimming, Ohio River Way
• Army Corps: Ohio waterborne commerce, 2023
• Ohio v. Kentucky, 444 U.S. 335 (1980)
• NTSB: Silver Bridge report, 1970
• USGS Water-Supply Paper 838, 1938 (PDF)
• NWS gauges: Cincinnati, Portsmouth, Marietta; NWS Ohio River Forecast Center
• ODNR GeoFacts 10; ODNR leaflet 7
• Ohio History Connection markers: 1-9, 6-41, 8-27, 8-73, 14-27, 16-53, 17-84, 30-25
• Latrobe, 1871; Hildreth, Pioneer History; Kellogg, 1917
• Northwest Ordinance (Avalon Project); Treaty of Greenville (Kappler)
• NHL nominations: survey beginning point, John Rankin House, John P. Parker House; NPS, 2018
• Brent Spence groundbreaking, 2026 and funding announcement, 2022; Brent Spence Bridge Corridor
• EIA Ohio tables, 2024 data; Census Bureau estimates, 2020-2024
• Ohio DOT byway map; City of Portsmouth; Ohio University; USFWS refuge
• AP via KSAT, 2022; Spectrum News, 2023; WCPO, 2023; Cincinnati Enquirer, 2011 (archived); roeblingbridge.org; Cincinnati Museum Center (archived)