| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Nashville | 1 | 2,992 | 3,093 | -0.63% | 964 | 3 | City |
| Okawville | 2 | 1,338 | 1,366 | -0.37% | 661 | 2 | Village |
| Irvington | 3 | 562 | 583 | -0.71% | 556 | 1 | Village |
| Hoyleton | 4 | 498 | 519 | -0.8% | 655 | 1 | Village |
| Ashley | 5 | 446 | 461 | -0.67% | 395 | 1 | City |
| Addieville | 6 | 255 | 257 | -0.39% | 257 | 1 | Village |
| Richview | 7 | 231 | 236 | -0.43% | 201 | 1 | Village |
| Oakdale | 8 | 197 | 197 | 0% | 125 | 2 | Village |
| Radom | 9 | 183 | 183 | 0% | 175 | 1 | Village |
| Du Bois | 10 | 179 | 181 | -0.56% | 170 | 1 | Village |
| Venedy | 11 | 124 | 127 | -0.8% | 441 | 0 | Village |
Nashville is the largest city in Washington County, with a population of 2,992.
Venedy is the smallest city in Washington County, with a population of 124.
There are 11 cities in Washington County, Illinois.