8 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| El Dorado | 1 | 16,135 | 17,700 | -1.59% | 996 | 16 | City |
| Smackover | 2 | 1,546 | 1,627 | -0.83% | 355 | 4 | City |
| Norphlet | 3 | 699 | 759 | -1.41% | 342 | 2 | City |
| Junction City | 4 | 469 | 501 | -1.05% | 413 | 1 | City |
| Huttig | 5 | 418 | 453 | -1.42% | 140 | 3 | City |
| Calion | 6 | 402 | 431 | -1.23% | 375 | 1 | City |
| Strong | 7 | 389 | 415 | -1.02% | 244 | 2 | City |
| Felsenthal | 8 | 83 | 86 | 0% | 56 | 1 | Town |
El Dorado is the largest city in Union County, with a population of 16,135.
Felsenthal is the smallest city in Union County, with a population of 83.
There are 8 cities in Union County, Arkansas.