11 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Nashville | 1 | 2,961 | 3,090 | -0.87% | 961 | 3.08 | City |
| Okawville | 2 | 1,341 | 1,366 | -0.37% | 662 | 2.02 | Village |
| Irvington | 3 | 562 | 582 | -0.71% | 556 | 1.01 | Village |
| Hoyleton | 4 | 496 | 518 | -0.8% | 653 | 0.76 | Village |
| Ashley | 5 | 444 | 461 | -0.67% | 394 | 1.13 | City |
| Addieville | 6 | 249 | 253 | -0.4% | 251 | 0.99 | Village |
| Richview | 7 | 227 | 236 | -0.87% | 198 | 1.15 | Village |
| Oakdale | 8 | 193 | 197 | -0.52% | 122 | 1.58 | Village |
| Du Bois | 9 | 181 | 178 | 0.56% | 172 | 1.05 | Village |
| Radom | 10 | 180 | 182 | 0% | 172 | 1.05 | Village |
| Venedy | 11 | 124 | 126 | 0% | 441 | 0.28 | Village |
Nashville is the largest city in Washington County, with a population of 2,961.
Venedy is the smallest city in Washington County.
There are 11 cities in Washington County, Illinois.