4 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Potosi | 1 | 2,538 | 2,543 | -0.04% | 1,090 | 2.33 | City |
| Irondale | 2 | 368 | 367 | 0% | 690 | 0.53 | City |
| Mineral Point | 3 | 230 | 225 | 0.44% | 958 | 0.24 | Town |
| Caledonia | 4 | 133 | 132 | 0% | 811 | 0.16 | Village |
Potosi is the largest city in Washington County, with a population of 2,538.
Caledonia is the smallest city in Washington County.
There are 4 cities in Washington County, Missouri.