TheMonongahela River (/məˌnɒŋɡəˈhiːlə/mə-NONG-gə-HEE-lə,/-ˈheɪ-/-⁠HAY-),^[10] sometimes referred to locally asthe Mon (/mɒn/),^[11] is a 130-mile-long (210 km)^[6]river on theAllegheny Plateau innorth-central West Virginia andSouthwestern Pennsylvania. The river flows from the confluence of itswest andeast forks in north-central West Virginia northeasterly into southwestern Pennsylvania, then northerly to Pittsburgh and its confluence with theAllegheny River to form theOhio River. The river includes a series of locks and dams that makes it navigable.

Monongahela River
The Monongahela River inPittsburgh withSouth Side Pittsburgh on the right andUptown Pittsburgh on the left
Map of the Monongahela River basin with the Monongahela River highlighted
Location
Country	United States
State	Pennsylvania andWest Virginia
Counties	Marion WV,Monongalia WV,Greene PA,Fayette PA,Washington PA,Westmoreland PA,Allegheny PA
Physical characteristics
Source	Tygart Valley River
• location	Pocahontas County,West Virginia
• coordinates	38°28′06″N79°58′51″W / 38.46833°N 79.98083°W /38.46833; -79.98083[1]
• elevation	4,540 ft (1,380 m)[2]
2nd source	West Fork River
• location	Upshur County,West Virginia
• coordinates	38°51′08″N80°21′32″W / 38.85222°N 80.35889°W /38.85222; -80.35889[3]
• elevation	1,309 ft (399 m)[4]
Source confluence
• location	Fairmont,West Virginia
• coordinates	39°27′53″N80°09′10″W / 39.46472°N 80.15278°W /39.46472; -80.15278[5]
• elevation	863 ft (263 m)[3]
Mouth	Ohio River
• location	Pittsburgh,Pennsylvania
• coordinates	40°26′30″N80°00′58″W / 40.44167°N 80.01611°W /40.44167; -80.01611[5]
• elevation	709 ft (216 m)[5]
Length	130 mi (210 km)[6]
Basin size	7,340 sq mi (19,000 km2)[7]
Discharge
• location	Braddock, PA[8]
• average	12,650 cu ft/s (358 m3/s)
• minimum	2,900 cu ft/s (82 m3/s)
• maximum	81,100 cu ft/s (2,300 m3/s)
Discharge
• location	Masontown, PA[9]
• average	8,433 cu ft/s (238.8 m3/s)
Basin features
Tributaries
• left	West Fork, Coal Run,Buffalo Creek, Hawkinberry Run,Paw Paw Creek, Pharoah Run, Parker Run, Indian Creek, Birchfield Run, Meadow Run, Broad Run, Dents Run, Scotts Run, Courtney Run, Robinson Run, Crooked Run,Dunkard Creek, Whiteley Creek, Little Whiteley Creek, Pegs Run, Muddy Creek, Noel Run,Pumpkin Run, Rush Run,Tenmile Creek, Fishpot Run, Barneys Run, Twomile Run, Lilly Run, Pike Run, Wood Run, Hooders Run, Maple Creek, Pigeon Creek, Dry Run, Mingo Creek, Huston Run, Lobbs Run,Peters Creek, Thompson Run, Homestead Run, West Run,Streets Run,Becks Run
• right	Tygart River, Prickett Creek, Little Creek, Whiteday Creek, Joes Run, Toms Run, Booths Run, Cobun Creek,Deckers Creek, West Run, Laurel Run, Camp Run,Cheat River,Georges Creek,Jacobs Creek, Cats Run, Browns Run, Middle Run, Antram Run, Wallace Run, Hereford Hollow, Bates Run, Meadow Run, Kelley Run, Rush Run, Dunlap Creek,Redstone Creek, Lamb Lick Run, Downers Run, Speers Run, Turkey Hollow, Beckers Run, Sunfish Run, Bunola Run, Kelly Run, Mill Run, Smiths Run, Fallen Timber Run, Wylie Run,Youghiogheny River,Crooked Run,Turtle Creek, Ninemile Run

TheUnami wordMonongahela means "falling banks", in reference to the geological instability of the river's banks.Moravian missionaryDavid Zeisberger (1721–1808) gave this account of the naming: "In theIndian tongue the name of this river wasMechmenawungihilla (alternatively spelledMenawngihella), which signifies a high bank, which is ever washed out and therefore collapses."^[12]

The Lenape Language Project renders the word asMënaonkihëla (pronounced[mənaoŋɡihəla]), translated "where banks cave in or erode",^[13] from the verbsmënaonkihële "the dirt caves off" (such as the bank of a river or creek, or in a landslide)^[14] andmënaonke (pronounced[mənaoŋɡe]), "it has a loose bank" (where one might fall in).^[15]

Monongalia County and the town ofMonongah, both in West Virginia, are named for the river, as is the city ofMonongahela in Pennsylvania. (The name "Monongalia" is either a Latinized adaptation of "Monongahela" or simply a variant spelling.)

TheUSGS name for the river is the Monongahela River; there have been numerous alternative names, alternative spellings and misspellings in historical texts.^[a]

The Monongahela is formed by the confluence of theWest Fork River and its "east fork"—theTygart Valley River—atFairmont in north central West Virginia. From there it flows northeasterly to cross the Pennsylvania border just west of northCheat Lake on itsCheat River tributary. Then it flows northerly across southwestern Pennsylvania, taking a bit of a detour northeast 10 miles south of Pittsburgh to approach Pittsburgh from the southeast and its confluence with theAllegheny River to form theForks of the Ohio at "The Point" ofPoint State Park inDowntown Pittsburgh.

Prior to early Pleistocene regional glaciation, more than 780,000 years ago, the ancestral Monongahela River (a.k.a. the Pittsburgh River) flowed northward from present-day north-central West Virginia, across westernPennsylvania and northwestern Ohio, and into theSaint Lawrence River watershed. One (or more) extensive ice sheet advance dammed the old north-flowing drainage and created a vast lake—known asLake Monongahela—stretching from an unknown point north of present-dayBeaver, Pennsylvania for ~200 miles (320 km) south toWeston, West Virginia. A river-lake with many narrow bays, its maximum water surface rose to 1,100 feet (340 m) above sea level. Over 200 feet (61 m) deep in places, its southwestward overflow gradually incised old drainage divides and contributed to the geological development of the present-day upperOhio River Valley.^[17][18]

Via the Ohio River, the river is part of the Mississippi watershed which drains to the Gulf of Mexico on the Atlantic Ocean.

The river's length is 130 miles, its drainage basin is 7,340 sq.mi. and the average 30-year discharge at Elizabeth, Pennsylvania, is 9,109 cfs. It falls 3,831 ft. in elevation from its highest source to its mouth on the Ohio River. It falls 280 feet from its forks to its mouth, a stretch made navigable by locks. The mean depth is about 20 ft.

In southwestern Pennsylvania, the Monongahela is met by two majortributaries: theCheat River, which joins atPoint Marion, and theYoughiogheny River, which joins atMcKeesport.

Major tributaries include:Becks Run,Big Sandy Creek,Buffalo Creek,Cheat River,Crooked Run,Deckers Creek,Dunkard Creek,Lick Run,Middle Fork River,Paw Paw Creek,Peters Creek,Streets Run,Turtle Creek,Tygart Valley River,West Fork River,Youghiogheny River.

The river is navigable its entire length with a series of locks and dams that maintain a minimum depth of 9 feet (2.7 m) to accommodate coal-laden barges. All dams are operated by the Pittsburgh District Army Corps of Engineers. In 2006, the navigation system, operated by theU.S. Army Corps of Engineers, had nine dam-locks along 128.7 miles (207.1 km) of waterway.^[19] The locks overcame a change in elevation of about 147 feet (44.8 m).^[20]

• Braddock Locks & Dam
• Locks & Dam 3
• Locks & Dam 4
• Maxwell Lock & Dam
• Grays Landing Lock & Dam
• Point Marion Lock and Dam
• Morgantown Lock and Dam
• Hildebrand Lock and Dam
• Opekiska Lock and Dam

The locks and dam at Elizabeth will be removed by the U.S. Army Corps of Engineers. Work will commence in 2024. Afterwards 30 miles of the river between Charleroi and Braddock will be free flowing.^[21]

According to the EPA's Toxics Release Inventory for 2010, the Monongahela ranked as the 17th most polluted river in the nation.^[22] The primary polluters were Pennsylvania iron and steel mills.

The upper drainage area of the river basin is renowned for its water sports/hobbies ofwhitewater kayaking (and in some caseswhitewater rafting) opportunities. The land here is of a very rugged plateau type which allows streams to gather sufficient water volume before they fall off the plateau and create challenging rapids. Some of the best known specific stream locations for this include:

• Youghiogheny River atOhiopyle, Pennsylvania^[23]
• Youghiogheny River atFriendsville, Maryland^[24]
• Cheat River atAlbright, West Virginia^[25][26]
• Tygart River atBelington, West Virginia^[27][28][29]

The Monongahela River valley was the site of a famous battle that was one of the first in theFrench and Indian War—theBraddock Expedition (May–July 1755). It resulted in a sharp defeat for two thousandBritish andColonial forces against those of theFrench and theirNative American allies.

In 1817, the Pennsylvania legislature authorized the Monongahela Navigation Company to build 16 dams with bypasslocks to create a river transportation system between Pittsburgh and the area that would later becomeWest Virginia.^[30] Originally planned to run as far south as theCheat River, the system was extended to Fairmont, andbituminous coal from West Virginia was the chief product transported downstream. After acanal tunnel through Grant's Hill in Pittsburgh was completed in 1832, boats could travel between the Monongahela River and the Western Division Canal of Pennsylvania's principal east–west canal and railroad system, theMain Line of Public Works. In 1897, the federal government took possession of the Monongahela Navigation throughcondemnation proceedings. Later, the dam-lock combinations were increased in size and reduced in number.^[20]

Briefly linked to the Monongahela Navigation was the Youghiogheny Navigation, a slack water system of 18.5 miles (29.8 km) between McKeesport andWest Newton. It had two dam-locks overcoming a change in elevation of about 27 feet (8.2 m). Opening in 1850, it was destroyed by a flood in 1865.^[20]

During the 19th century and well into the twentieth, the Monongahela was heavily used byindustry, and severalU.S. Steel plants, including theHomestead Works, site of theHomestead Strike of 1892, were built along its banks. Following the killing of several workers in the course of the strike, anarchistEmma Goldman wrote: "Words had lost their meaning in the face of the innocent blood spilled on the banks of the Monongahela." Other mills included theEdgar Thomson Works inBraddock, the first steel works in the area, theDuquesne Works and theJones and Laughlin steel works on the South Side of Pittsburgh. Only the Edgar Thomson works remain producing steel along the river.

Despite the closure of many of the mills in the 1980s and 90s, the Monogahela is still an important waterway for industry. TheMon Valley Works of U.S. Steel operates three plants, including the Edgar Thomson plant for basic steel marking, theIrvin plant for steel finishing, and theClairton plant for coke production.^[31] Coal barges are a common sight on the river, and the railways which line either side are heavily used by freight. Other industries include power generation, chemicals, and recycling.

Three ships in theUnited States Navy have been namedMonongahela after the river.In October 1930, severe drought caused the river flow to drop below 10 cu ft/s (280 L/s), and in some places, it was possible to walk across the river bottom.^{[citation needed]}

The river was the site of afamous airplane crash that has become the subject ofurban legends andconspiracy theories. Early on the morning of January 31, 1956, aB-25 bomber en route fromNellis Air Force Base inNevada toOlmsted Air Force Base in Pennsylvania crashed into the river near theGlenwood Bridge inHomestead, Pennsylvania. The six crewmen survived the initial crash, but two of them succumbed in thecold water and drowned. Despite the relatively shallow water, the aircraft was never recovered and became known as the "ghost bomber".^[32][33] ThePittsburgh Post-Gazette published a graphical representation of the flight path and flight details in 1999.^[34][35] As of 2018, the bomber has not been found.

•  
  TheSouth Tenth Street Bridge over the Monongahela River inPittsburgh in 2005
•  
  The Monongahela River inFairmont, West Virginia, in 2006
•  
  Monongahela River Scene, 1857^[36]
•  
  Opekiska Lock and Dam on the Monongahela River nearFairmont, West Virginia, atriver mile 115 (185 km)
•  
  Monongahela River inPittsburgh in 2021

• List of crossings of the Monongahela River
• List of rivers of Pennsylvania
• List of rivers of West Virginia
• Geography of Pennsylvania

• Bissell, Richard (1952),The Monongahela,Rinehart & Co.
• Callahan, James Morton and Bernard Lee Butcher (1912),Genealogical and Personal History of the Upper Monongahela Valley, West Virginia,New York: Lewis Historical Publishing Company.
• Core, Earl L. (1984), "The Monongalia River," in: Bartlett, Richard A. (ed),Rolling Rivers: An Encyclopedia of America's Rivers. New York: McGraw-Hill.ISBN 0-07-003910-0. pp 149–52.
• Core, Earl L. (1974–84),The Monongalia Story: A Bicentennial History,Parsons, W.Va.:McClain Printing Co., 5 volumes; an extensive, well-documented natural & human history of the Monongahela River basin.
  • Volume I:Prelude (1974)
  • Volume II:The Pioneers (1976)
  • Volume III:Discord (1979)
  • Volume IV:Industrialization (1984)
  • Volume V:Sophistication (1984)

• U.S. Geological Survey: PA stream gaging stations
• Beach, Chandler B., ed. (1914)."Monongahela" .The New Student's Reference Work . Chicago: F. E. Compton and Co.