Monongalia County, known locally as Mon County, is a county located in the U.S. state of West Virginia. As of the 2020 census, the population was 105,822, making it West Virginia's third-most populous county. Its county seat is Morgantown. The county was founded in 1776. Monongalia County is included in the Morgantown, WV Metropolitan Statistical Area, and is the largest county in North-Central West Virginia. It is part of the Pittsburgh media market.

Monongalia County takes its name from the Monongahela River. The name Monongalia may be a misspelling of Monongahela. Alternatively, the conventional Latinate ending "-ia" (designating "land of..." or "country of..." — as in Arabia, Bolivia or Colombia) may have been added to Monongahela (i.e., "Land of the Monongahela").

Monongalia County was formed in 1776 when Virginia's remote District of West Augusta was divided into three counties: Ohio, Yohogania and Monongalia, all named for their most prominent rivers. Ohio County then encompassed most of the western region of the district bordering the Ohio River, including parts of what is now southwestern Pennsylvania. Yohogania County consisted of much of what is now southwestern Pennsylvania and the present counties of Hancock and the northern part of Brooke in West Virginia. Monongalia County also encompassed what are now the counties of Tucker, Randolph, Marion, Harrison and Barbour in north-central West Virginia, as well as parts of what are now Washington, Greene and Fayette Counties in Pennsylvania. In 1780, in his Notes on the State of Virginia, Thomas Jefferson gave the militia enrollment of what was then the vast Monongalia County at 1,000 troops.

In 1863, West Virginia's counties were divided into civil townships, with the intention of encouraging local government. This proved impractical in the heavily rural state, and in 1872 the townships were converted into magisterial districts. Monongalia County was divided into seven districts: Battelle, Cass, Clay, Clinton, Grant, Morgan, and Union. After a century of relative stability, in the 1970s Monongalia's seven historic magisterial districts were consolidated into three new Districts: Central, Eastern, and Western.

This section needs expansion. You can help by adding to it. (June 2011)

• Fayette County, Pennsylvania (northeast)
• Greene County, Pennsylvania (north)
• Marion County (south)
• Preston County (east)
• Taylor County (southeast)
• Wetzel County (west)

• I-68
• I-79
• US 19
• US 119
• WV 7
• WV 43
• WV 100
• WV 218
• WV 705

• Aarons Creek
• Cam Harker Spring
• Cheat Lake
• Cheat River
• Deckers Creek
• Dunkard Creek
• Jakes Run
• Monongahela River

• Henderson Ridge

Historical population

Census	Pop.	Note	%±
1790	4,768		—
1800	8,540		79.1%
1810	12,793		49.8%
1820	11,060		−13.5%
1830	14,056		27.1%
1840	17,368		23.6%
1850	12,387		−28.7%
1860	13,048		5.3%
1870	13,547		3.8%
1880	14,985		10.6%
1890	15,705		4.8%
1900	19,049		21.3%
1910	24,334		27.7%
1920	33,618		38.2%
1930	50,083		49.0%
1940	51,252		2.3%
1950	60,797		18.6%
1960	55,617		−8.5%
1970	63,714		14.6%
1980	75,024		17.8%
1990	75,509		0.6%
2000	81,866		8.4%
2010	96,189		17.5%
2020	105,822		10.0%
2021 (est.)	106,387		0.5%
U.S. Decennial Census 1790–1960 1900–1990 1990–2000 2010–2020

As of the 2020 census, there were 105,882 people and 42,710 households residing in the city. There were 49,881 housing units in Monongalia County. The racial makeup of the county was 85% White, 3.9% African American, 3.5% Asian, 0.2% Native American, 1.1% from other races, and 6.1% from two or more races. Hispanics or Latinos of any race were 3.1% of the population.

There were 42,710 households, of which 41% were married couples living together, 25.4% had a male householder with no spouse present, 25.3% had a female householder with no spouse present.The average household and family size was 3.06. The median age in the county was 33 years. The median income for a household in the county was $56,374.

As of the 2010 United States census, there were 96,189 people, 39,777 households, and 20,032 families living in the county. The population density was 267.1 inhabitants per square mile (103.1/km). There were 43,238 housing units at an average density of 120.1 per square mile (46.4/km). The racial makeup of the county was 91.0% white, 3.6% black or African American, 3.1% Asian, 0.2% American Indian, 0.4% from other races, and 1.8% from two or more races. Those of Hispanic or Latino origin made up 1.8% of the population. In terms of ancestry, 25.7% were German, 17.1% were Irish, 13.0% were English, 11.0% were Italian, 7.5% were American, and 5.0% were Polish.

Of the 39,777 households, 22.0% had children under the age of 18 living with them, 38.3% were married couples living together, 8.2% had a female householder with no husband present, 49.6% were non-families, and 31.7% of all households were made up of individuals. The average household size was 2.24 and the average family size was 2.87. The median age was 29.1 years.

The median income for a household in the county was $39,167 and the median income for a family was $62,966. Males had a median income of $43,383 versus $32,164 for females. The per capita income for the county was $23,116. About 8.6% of families and 21.0% of the population were below the poverty line, including 13.2% of those under age 18 and 7.6% of those age 65 or over.

As of the census of 2000, there were 81,866 people, 33,446 households, and 18,495 families living in the county. The population density was 227 people per square mile (88 people/km). There were 36,695 housing units at an average density of 102 per square mile (39/km). The racial makeup of the county was 92.22% White, 3.38% Black or African American, 0.20% Native American, 2.45% Asian, 0.04% Pacific Islander, 0.32% from other races, and 1.39% from two or more races. 1.01% of the population were Hispanic or Latino of any race.

There were 33,446 households, out of which 24.20% had children under the age of 18 living with them, 43.80% were married couples living together, 8.30% had a female householder with no husband present, and 44.70% were non-families. 31.30% of all households were made up of individuals, and 8.40% had someone living alone who was 65 years of age or older. The average household size was 2.28 and the average family size was 2.91.

In the county, the population was spread out, with 18.20% under the age of 18, 23.40% from 18 to 24, 27.70% from 25 to 44, 20.00% from 45 to 64, and 10.70% who were 65 years of age or older. The median age was 30 years. For every 100 females, there were 101.80 males. For every 100 females age 18 and over, there were 101.20 males.

The median income for a household in the county was $28,625, and the median income for a family was $43,628. Males had a median income of $33,113 versus $23,828 for females. The per capita income for the county was $17,106. About 11.30% of families and 22.80% of the population were below the poverty line, including 17.90% of those under age 18 and 8.00% of those age 65 or over.

The county government consists of a county commission with three members. Currently, these members are: Thomas Bloom (D), Sean Sikora (R) and Jeffery Arnett (D). While still typically favoring Republicans, the county tends to lean significantly more Democratic than the rest of West Virginia.

In the 20th century, Monongalia County had been a bellwether for West Virginia, voting the same as the state in every election from 1916 to 2024, even as the candidate lost the national election, with the sole exception of 2008 when Barack Obama won the county and lost the state. Donald Trump carried the county with just over 500 more votes than Democrat Joe Biden in the 2020 presidential election, by far Biden's best county-level performance in the state.

Its competitiveness is due to its seat, Morgantown, home of the West Virginia University, being solidly Democratic and the county's rural precincts being solidly Republican. The rural precincts are slightly more populous, resulting in the county's Republican tilt.

United States presidential election results for Monongalia County, West Virginia

Year	Republican		Democratic		Third party(ies)
	No.	%	No.	%	No.	%
2024	21,084	50.56%	19,265	46.20%	1,349	3.24%
2020	20,803	49.44%	20,282	48.20%	994	2.36%
2016	18,432	50.13%	14,699	39.97%	3,641	9.90%
2012	16,831	53.28%	13,826	43.77%	934	2.96%
2008	15,775	46.99%	17,060	50.82%	734	2.19%
2004	17,670	51.51%	16,313	47.55%	323	0.94%
2000	13,595	49.68%	12,603	46.05%	1,169	4.27%
1996	10,189	37.99%	13,406	49.99%	3,225	12.02%
1992	9,831	34.35%	14,142	49.41%	4,650	16.25%
1988	12,091	45.91%	14,178	53.83%	69	0.26%
1984	14,972	52.95%	13,236	46.81%	66	0.23%
1980	11,972	43.02%	12,883	46.30%	2,971	10.68%
1976	11,827	42.25%	16,163	57.75%	0	0.00%
1972	16,758	60.98%	10,721	39.02%	0	0.00%
1968	9,261	38.68%	13,128	54.83%	1,556	6.50%
1964	6,473	27.16%	17,358	72.84%	0	0.00%
1960	11,523	46.79%	13,103	53.21%	0	0.00%
1956	14,046	56.05%	11,016	43.95%	0	0.00%
1952	13,111	49.92%	13,152	50.08%	0	0.00%
1948	9,329	43.02%	12,138	55.98%	216	1.00%
1944	9,647	48.05%	10,429	51.95%	0	0.00%
1940	10,367	44.48%	12,940	55.52%	0	0.00%
1936	8,811	39.02%	13,677	60.57%	94	0.42%
1932	8,417	43.79%	10,319	53.69%	485	2.52%
1928	11,364	64.08%	6,182	34.86%	188	1.06%
1924	6,994	49.57%	4,977	35.27%	2,139	15.16%
1920	6,773	63.99%	3,442	32.52%	369	3.49%
1916	3,412	57.48%	2,227	37.52%	297	5.00%
1912	1,216	23.20%	1,673	31.92%	2,352	44.88%

The county's public schools are operated by Monongalia County Schools. The county is also home to West Virginia's largest university, West Virginia University, located in Morgantown.

• Morgantown (county seat)
• Westover

• Blacksville
• Granville
• Star City

• Central
• Eastern
• Western

• Brookhaven
• Cassville
• Cheat Lake
• Pentress

• National Register of Historic Places listings in Monongalia County, West Virginia
• Snake Hill Wildlife Management Area
• West Virginia University
• Murder of Skylar Neese

• Core, Earl Lemley, The Monongalia Story: A Bicentennial History, Vol. I: Prelude (1974), Parsons, W.Va.: McClain Printing Co.
• Core, Earl Lemley, The Monongalia Story: A Bicentennial History, Vol. II: The Pioneers (1976), Parsons, W.Va.: McClain Printing Co.
• Core, Earl Lemley, The Monongalia Story: A Bicentennial History, Vol. III: Discord (1979), Parsons, W.Va.: McClain Printing Co.
• Core, Earl Lemley, The Monongalia Story: A Bicentennial History, Vol. IV: Industrialization (1984), Parsons, W.Va.: McClain Printing Co.
• Core, Earl Lemley, The Monongalia Story: A Bicentennial History, Vol. V: Sophistication (1984), Parsons, W.Va.: McClain Printing Co.

• Official website
• Monongalia County History

39°38′N 80°03′W / 39.63°N 80.05°W / 39.63; -80.05