County outline
Where Allendale County is located
Area breakdown
Land accounts for 99% of Allendale County’s measured area and water for 1%. Its combined area converts to 1,068.2 square kilometers or approximately 263,947 acres.
Green: land · blue: water
| Measurement | Square miles | Square kilometers | Acres |
|---|---|---|---|
| Land | 408.099 | 1,056.972 | 261,183.4 |
| Water | 4.318 | 11.184 | 2,763.5 |
| Total | 412.417 | 1,068.155 | 263,946.9 |
How Allendale County compares
By original Census land area, Allendale County ranks #41 of 46 in South Carolina and #2479 of 3,222 nationally. National rankings include the 50 states, District of Columbia, and Puerto Rico.
Its land area is 0.662 times the South Carolina county-equivalent median of 616.9 square miles. It accounts for 1.4% of the combined county land area in the state.
See the complete South Carolina ranking · What counts as a county equivalent?
Population and density of Allendale County
The Census Bureau estimates that 7,355 people lived in Allendale County on July 1, 2025. That ranks #2,707 of 3,222 county equivalents nationally and #46 of 46 in South Carolina. Since the April 1, 2020 estimates base of 8,037, the population has declined by 682 (−8.5%), compared with +8.8% for South Carolina as a whole.
With 408.1 square miles of land, that is 18 people per square mile (7 per km²), placing Allendale County #2,385 nationally for density and #46 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 36 acres of land per resident.
| July 1 | 2020 | 2021 | 2022 | 2023 | 2024 | 2025 |
|---|---|---|---|---|---|---|
| Estimate | 7,940 | 7,710 | 7,510 | 7,588 | 7,531 | 7,355 |
| Change | — | −230 | −200 | +78 | −57 | −176 |
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 Allendale County
4 incorporated places lie at least partly in Allendale County. Together they are home to 3,972 people (54%); the other 3,383 (46%) live outside any incorporated place, in unincorporated communities and rural areas.
The largest is Allendale town, with 2,427 residents in the county.
| Incorporated place | Population 2025 | Since 2020 | Land mi² |
|---|---|---|---|
| Allendale townCounty seat | 2,427 | −10% | 3.26 |
| Fairfax town | 1,352 | −9.5% | 3.213 |
| Sycamore town | 138 | −9.2% | 3.053 |
| Ulmer town | 55 | −11.3% | 3.061 |
Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside Allendale County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.
Metropolitan area
Allendale 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
6 ZIP Code Tabulation Areas have land in Allendale County; 5 of them have most of their land inside the county, and the others mainly cover neighboring areas.
298102981229827298362984929932
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 Allendale County
Allendale County shares a land border with 5 county equivalents, including 2 in Georgia. It has more land than 1 of them. The largest neighbor is Burke County (827 mi²) and the smallest is Bamberg County (393.4 mi²). Together with its neighbors, Allendale County forms a block of 3,382.7 mi² of land, of which it holds 12.1%.
| Bordering county equivalent | Land mi² | Size vs. Allendale | Compare |
|---|---|---|---|
| Burke CountyGeorgia | 827 | 2× larger | Compare |
| Screven CountyGeorgia | 645.8 | 1.6× larger | Compare |
| Hampton County | 560 | 1.4× larger | Compare |
| Barnwell County | 548.4 | 1.3× larger | Compare |
| Bamberg County | 393.4 | about the same | Compare |
How big is Allendale County compared with U.S. states?
Allendale County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.5 times as much. South Carolina’s county land could hold about 74 areas the size of Allendale County.
Another way to picture it: the same land area would fill a square about 20.2 miles (32.5 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 Allendale County?
Allendale County has more land than 743 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 Allendale County at #2,528 nationally by total area, 49 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% — 0.1 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 Allendale County in the national ranking. They can be in different states and are not necessarily geographic neighbors.
| Land rank | County equivalent | Land mi² | Comparison |
|---|---|---|---|
| #2478 | Jefferson County, Ohio | 408.1 | Compare |
| #2479 | Allendale County, South Carolina | 408.1 | This county |
| #2480 | Forsyth County, North Carolina | 408 | 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 32.979757, -81.363265. 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: 1,056,971,531 m²; AWATER: 11,183,482 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 Allendale County?
Allendale County, South Carolina has 408.1 square miles (1,057 km²) of land and 4.318 square miles of water, for a total area of 412.4 square miles. It ranks #2479 of 3,222 U.S. county equivalents by land area.
Is Allendale County the largest county in South Carolina?
No. Allendale County ranks #41 of 46 in South Carolina by land area. The largest is Horry County, with 1,133.1 square miles of land.
What counties border Allendale County?
Allendale County shares a land border with Hampton County, Barnwell County, Screven County, Georgia, Bamberg County, and Burke County, Georgia.
What is the population of Allendale County?
The Census Bureau estimates Allendale County had 7,355 residents on July 1, 2025, ranking #2,707 of 3,222 county equivalents. That is 18 people per square mile of land.
What is the county seat of Allendale County?
The county seat of Allendale County is Allendale.
What cities and towns are in Allendale County?
Allendale County has 4 incorporated places. The most populous are Allendale town, Fairfax town, Sycamore town, and Ulmer town; 3,383 residents live outside any incorporated place.
Is Allendale County part of a metropolitan area?
No. Allendale County is outside every metropolitan and micropolitan statistical area in the July 2023 OMB delineation.
How many ZIP codes are in Allendale County?
6 ZIP Code Tabulation Areas have land in Allendale County, and 5 of them have most of their land inside the county. Census ZIP Code Tabulation Areas approximate USPS ZIP Code areas.
How does Allendale County compare with U.S. states?
It has less land than every state. Rhode Island, the smallest, has 2.5 times as much land.
How many acres of land are in Allendale County?
The land measurement converts to approximately 261,183 acres. Including water, total area is approximately 263,947 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.