5 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Barnwell | 1 | 4,531 | 4,646 | -0.51% | 578 | 8 | City |
| Williston | 2 | 2,841 | 2,890 | -0.35% | 317 | 9 | Town |
| Blackville | 3 | 1,894 | 1,926 | -0.32% | 212 | 9 | Town |
| Hilda | 4 | 423 | 420 | 0.24% | 138 | 3 | Town |
| Elko | 5 | 141 | 140 | 0% | 134 | 1 | Town |
Barnwell is the largest city in Barnwell County, with a population of 4,531.
Elko is the smallest city in Barnwell County, with a population of 141.
There are 5 cities in Barnwell County, South Carolina.