thumb|New Monongalia County Justice Center in 2017
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.
History
left|145px|thumb|Map of Ohio, Monongalia, & Yohogania Counties circa 1776. Monongalia County is in magenta.
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.
thumb|Forks-Of-Cheat Baptist Church sign on Stewartstown Road, reflecting the region's early beginnings.
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.
Geography
Adjacent counties
- Fayette County, Pennsylvania (northeast)
- Greene County, Pennsylvania (north)
- Marion County (south)
- Preston County (east)
- Taylor County (southeast)
- Wetzel County (west)
Major highways
Rivers, streams, and lakes
- Aarons Creek
- Cam Harker Spring
- Cheat Lake
- Cheat River
- Deckers Creek
- Dunkard Creek
- Jakes Run
- Monongahela River
Ridges and valleys
- Berry Hollow
- Henderson Ridge