4 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Lake Butler | 1 | 18,356 | 17,700 | 1.08% | 1,610 | 11 | CDP |
| Lake Butler | 2 | 1,984 | 1,978 | 0.05% | 841 | 2 | City |
| Worthington Springs | 3 | 380 | 377 | 0% | 396 | 1 | Town |
| Raiford | 4 | 225 | 218 | 0.45% | 413 | 1 | Town |
Lake Butler is the largest city in Union County, with a population of 18,356.
Raiford is the smallest city in Union County, with a population of 225.
There are 4 cities in Union County, Florida.