4 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Union | 1 | 7,874 | 8,215 | -0.72% | 985 | 8 | City |
| Jonesville | 2 | 798 | 848 | -0.99% | 786 | 1 | Town |
| Lockhart | 3 | 363 | 383 | -0.82% | 1,190 | 0 | Town |
| Carlisle | 4 | 313 | 319 | -0.32% | 221 | 1 | Town |
Union is the largest city in Union County, with a population of 7,874.
Carlisle is the smallest city in Union County, with a population of 313.
There are 4 cities in Union County, South Carolina.