4 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Union | 1 | 7,931 | 8,215 | -0.71% | 992 | 8 | City |
| Jonesville | 2 | 806 | 848 | -1.1% | 794 | 1 | Town |
| Lockhart | 3 | 366 | 383 | -1.08% | 1,200 | 0 | Town |
| Carlisle | 4 | 314 | 319 | -0.32% | 222 | 1 | Town |
Union is the largest city in Union County, with a population of 7,931.
Carlisle is the smallest city in Union County, with a population of 314.
There are 4 cities in Union County, South Carolina.