County outline
Where Marion County is located
Area breakdown
Land accounts for 99.1% of Marion County’s measured area and water for 0.9%. Its combined area converts to 806.8 square kilometers or approximately 199,372 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 308.785 | 799.749 | 197,622.4 |
| Water | 2.733 | 7.078 | 1,749.1 |
| Total | 311.518 | 806.828 | 199,371.5 |
How Marion County compares
By original Census land area, Marion County ranks #43 of 55 in West Virginia and #2791 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.737 times the West Virginia county-equivalent median of 419 square miles. It accounts for 1.3% of the combined county land area in the state.
See the complete West Virginia ranking · What counts as a county equivalent?
Population and density of Marion County
The Census Bureau estimates that 55,584 people lived in Marion County on July 1, 2025. That ranks #955 of 3,222 county equivalents nationally and #11 of 55 in West Virginia. Since the April 1, 2020 estimates base of 56,215, the population has declined by 631 (−1.1%), compared with −1.5% for West Virginia as a whole.
With 308.8 square miles of land, that is 180 people per square mile (70 per km²), placing Marion County #681 nationally for density and #10 in West Virginia. The median county equivalent has 47 people per square mile; the West Virginia median is 45. Put another way, there are about 3.6 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 56,240 | 56,068 | 55,806 | 55,826 | 55,685 | 55,584 |
| Change | — | −172 | −262 | +20 | −141 | −101 |
U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.
Cities and towns in Marion County
11 incorporated places lie at least partly in Marion County. Together they are home to 28,761 people (51.7%); the other 26,823 (48.3%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Fairmont city, with 18,035 residents in the county.
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Fairmont cityCounty seat | 18,035 | −2.1% | 8.601 |
| Pleasant Valley city | 3,457 | −1.1% | 3.231 |
| Mannington city | 1,910 | −2.4% | 1.093 |
| Barrackville town | 1,196 | −1.2% | 0.689 |
| Monongah town | 1,055 | +9.3% | 0.488 |
| Rivesville town | 806 | −2.3% | 0.524 |
| White Hall town | 700 | −0.7% | 1.052 |
| Grant Town town | 669 | −2.3% | 0.527 |
| Farmington town | 395 | +1.5% | 0.415 |
| Fairview town | 367 | −1.3% | 0.28 |
| Worthington town | 171 | −2.3% | 0.583 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Marion County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Marion County is a central county of the Fairmont, WV Micropolitan Statistical Area. Marion County is the area’s only county equivalent, so the micro area has the same 308.8 square miles of land. By combined land it ranks #523 of 542 micropolitan areas, and #190 by population. It belongs to the Fairmont-Clarksburg, WV Combined Statistical Area.
ZIP codes
18 ZIP Code Tabulation Areas have land in Marion County; 14 of them have most of their land inside the county, and the others mainly cover neighboring areas.
263542643726448265542655926560265632657026571265722657426576265822658526586265872658826591
ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.
Counties bordering Marion County
Marion County shares a land border with 4 county equivalents. It has more land than 1 of them. The largest neighbor is Harrison County (416 mi²) and the smallest is Taylor County (172.8 mi²). Together with its neighbors, Marion County forms a block of 1,615.7 mi² of land, of which it holds 19.1%.
| Bordering county equivalent | Land mi² | Size vs. Marion | Compare |
|---|---|---|---|
| Harrison County | 416 | 1.3× larger | Compare |
| Monongalia County | 360.1 | 1.2× larger | Compare |
| Wetzel County | 358.1 | 1.2× larger | Compare |
| Taylor County | 172.8 | 1.8× smaller | Compare |
How big is Marion County compared with U.S. states?
Marion County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 3.3 times as much. West Virginia’s county land could hold about 78 areas the size of Marion County.
Another way to picture it: the same land area would fill a square about 17.6 miles (28.3 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.
State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.
What stands out about Marion County?
Marion County has more land than 431 of the other 3,221 county equivalents in the dataset.
A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.
Does including water change its rank?
Using land plus water places Marion County at #2,823 nationally by total area, 32 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.
Its water share is 0.9%, compared with a national county-equivalent median of 1.2% — 0.3 percentage points lower. This describes the statistical geography’s land/water mix, not flood exposure or developable land.
Closest positions in the national land ranking
These entries sit immediately beside Marion County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #2790 | Steuben County, Indiana | 308.8 | Compare |
| #2791 | Marion County, West Virginia | 308.8 | This county |
| #2792 | Magoffin County, Kentucky | 308.4 | Compare |
Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.
Representative coordinates
The Census internal point is 39.505839, -80.243402. It represents a location inside the geography; it is not necessarily the centroid or the address of a courthouse.
Source and precision
U.S. Census Bureau, 2026 Gazetteer Files, Counties. Original ALAND: 799,749,333 m²; AWATER: 7,079,302 m². Rankings use ALAND; exact ties use ascending GEOID. Tables preserve Census-published square miles to three decimals, with conversions based on those values.
Common questions
How big is Marion County?
Marion County, West Virginia has 308.8 square miles (799.7 km²) of land and 2.733 square miles of water, for a total area of 311.5 square miles. It ranks #2791 of 3,222 U.S. county equivalents by land area.
Is Marion County the largest county in West Virginia?
No. Marion County ranks #43 of 55 in West Virginia by land area. The largest is Randolph County, with 1,039.7 square miles of land.
What counties border Marion County?
Marion County shares a land border with Monongalia County, Harrison County, Taylor County, and Wetzel County.
What is the population of Marion County?
The Census Bureau estimates Marion County had 55,584 residents on July 1, 2025, ranking #955 of 3,222 county equivalents. That is 180 people per square mile of land.
What is the county seat of Marion County?
The county seat of Marion County is Fairmont.
What cities and towns are in Marion County?
Marion County has 11 incorporated places. The most populous five are Fairmont city, Pleasant Valley city, Mannington city, Barrackville town, and Monongah town; 26,823 residents live outside any incorporated place.
Is Marion County part of a metropolitan area?
Yes. It is a central county of the Fairmont, WV Micropolitan Statistical Area.
How many ZIP codes are in Marion County?
18 ZIP Code Tabulation Areas have land in Marion County, and 14 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Marion County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 3.3 times as much land.
How many acres of land are in Marion County?
The land measurement converts to approximately 197,622 acres. Including water, total area is approximately 199,372 acres. One square mile equals 640 acres.
Why might another source show a different area?
Check whether it reports land or total area, its Census vintage, and its rounding. Our guide explains how to reconcile county area figures.
Can this establish a property boundary?
No. Statistical measurements and generalized maps do not establish property lines. Consult the relevant local surveying or land-records authority.