| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Barnwell | 1 | 4,606 | 4,648 | -0.28% | 587 | 8 | City |
| Williston | 2 | 2,895 | 2,890 | -0.1% | 323 | 9 | Town |
| Blackville | 3 | 1,921 | 1,927 | -0.21% | 215 | 9 | Town |
| Hilda | 4 | 425 | 420 | 0% | 138 | 3 | Town |
| Elko | 5 | 140 | 137 | 0% | 133 | 1 | Town |
Barnwell is the largest city in Barnwell County, with a population of 4,606.
Elko is the smallest city in Barnwell County, with a population of 140.
There are 5 cities in Barnwell County, South Carolina.