| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Union | 1 | 8,033 | 8,211 | -0.54% | 1,005 | 8 | City |
| Jonesville | 2 | 810 | 851 | -0.86% | 798 | 1 | Town |
| Lockhart | 3 | 366 | 380 | -0.81% | 1,200 | 0 | Town |
| Carlisle | 4 | 319 | 321 | -0.31% | 225 | 1 | Town |
Union is the largest city in Union County, with a population of 8,033.
Carlisle is the smallest city in Union County, with a population of 319.
There are 4 cities in Union County, South Carolina.