5 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Barnwell | 1 | 4,573 | 4,650 | -0.35% | 583 | 8 | City |
| Williston | 2 | 2,875 | 2,895 | -0.14% | 321 | 9 | Town |
| Blackville | 3 | 1,901 | 1,925 | -0.26% | 213 | 9 | Town |
| Hilda | 4 | 421 | 419 | 0% | 137 | 3 | Town |
| Elko | 5 | 140 | 139 | 0% | 133 | 1 | Town |
Barnwell is the largest city in Barnwell County, with a population of 4,573.
Elko is the smallest city in Barnwell County, with a population of 140.
There are 5 cities in Barnwell County, South Carolina.