11 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Nashville | 1 | 2,960 | 3,097 | -0.77% | 953 | 3 | City |
| Okawville | 2 | 1,337 | 1,366 | -0.37% | 660 | 2 | Village |
| Irvington | 3 | 558 | 582 | -0.71% | 552 | 1 | Village |
| Hoyleton | 4 | 498 | 519 | -0.6% | 655 | 1 | Village |
| Ashley | 5 | 441 | 459 | -0.68% | 391 | 1 | City |
| Addieville | 6 | 251 | 257 | -0.4% | 253 | 1 | Village |
| Richview | 7 | 228 | 236 | -0.44% | 198 | 1 | Village |
| Oakdale | 8 | 197 | 197 | 0% | 125 | 2 | Village |
| Radom | 9 | 180 | 183 | 0% | 172 | 1 | Village |
| Du Bois | 10 | 179 | 178 | 0% | 170 | 1 | Village |
| Venedy | 11 | 122 | 125 | 0% | 434 | 0 | Village |
Nashville is the largest city in Washington County, with a population of 2,960.
Venedy is the smallest city in Washington County, with a population of 122.
There are 11 cities in Washington County, Illinois.