Marion County area

Population and density of Marion County

The Census Bureau estimates that 28,242 people lived in Marion County on July 1, 2025. That ranks #1,545 of 3,222 county equivalents nationally and #33 of 46 in South Carolina. Since the April 1, 2020 estimates base of 29,184, the population has declined by 942 (−3.2%), compared with +8.8% for South Carolina as a whole.

With 489.4 square miles of land, that is 58 people per square mile (22 per km²), placing Marion County #1,416 nationally for density and #29 in South Carolina. The median county equivalent has 47 people per square mile; the South Carolina median is 78. Put another way, there are about 11 acres of land per resident.

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

4 incorporated places lie at least partly in Marion County. Together they are home to 10,234 people (36.2%); the other 18,008 (63.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Marion city, with 6,028 residents in the county.

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 not part of any metropolitan or micropolitan statistical area in the Office of Management and Budget’s July 2023 delineation; 1,306 other county equivalents are also outside one. These areas are built around an urban core of at least 10,000 people plus the counties tied to it by commuting, so counties outside them are generally rural.

ZIP codes

8 ZIP Code Tabulation Areas have land in Marion County; 6 of them have most of their land inside the county, and the others mainly cover neighboring areas.

2951929546295652957129574295812958929592

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 5 county equivalents. It has more land than 1 of them. The largest neighbor is Horry County (1,133.1 mi²) and the smallest is Dillon County (405.1 mi²). Together with its neighbors, Marion County forms a block of 4,575.7 mi² of land, of which it holds 10.7%.

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 2.1 times as much. South Carolina’s county land could hold about 61 areas the size of Marion County.

Another way to picture it: the same land area would fill a square about 22.1 miles (35.6 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 1,094 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 #2,207 nationally by total area, 79 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 1%, compared with a national county-equivalent median of 1.2% — 0.2 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.

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.