7 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Fort Atkinson | 1 | 12,276 | 12,579 | -0.41% | 2,100 | 6 | City |
| Jefferson | 2 | 7,757 | 7,784 | -0.05% | 1,330 | 6 | City |
| Lake Mills | 3 | 6,793 | 6,265 | 1.31% | 1,626 | 4 | City |
| Waterloo | 4 | 3,668 | 3,496 | 0.8% | 967 | 4 | City |
| Johnson Creek | 5 | 3,426 | 3,341 | 0.41% | 1,131 | 3 | Village |
| Palmyra | 6 | 1,715 | 1,727 | -0.12% | 749 | 2 | Village |
| Sullivan | 7 | 653 | 652 | 0% | 576 | 1 | Village |
Fort Atkinson is the largest city in Jefferson County, with a population of 12,276.
Sullivan is the smallest city in Jefferson County, with a population of 653.
There are 7 cities in Jefferson County, Wisconsin.