21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rock Creek | 1 | 2,787 | 2,778 | 0.22% | 52 | 54 | Township |
| Oskaloosa | 2 | 2,154 | 2,162 | -0.05% | 38 | 57 | Township |
| Delaware | 3 | 1,786 | 1,812 | -0.33% | 20 | 88 | Township |
| Union | 4 | 1,649 | 1,661 | 0.12% | 39 | 42 | Township |
| Ozawkie | 5 | 1,648 | 1,646 | 0.12% | 44 | 38 | Township |
| Kentucky | 6 | 1,548 | 1,539 | 0.32% | 43 | 36 | Township |
| Kaw | 7 | 1,405 | 1,386 | 0.36% | 44 | 32 | Township |
| Oskaloosa | 8 | 1,066 | 1,098 | -0.65% | 1,072 | 1 | City |
| Jefferson | 9 | 1,065 | 1,071 | -0.09% | 18 | 58 | Township |
| Valley Falls | 10 | 1,059 | 1,091 | -0.66% | 1,504 | 1 | City |
| Sarcoxie | 11 | 1,002 | 988 | 0.4% | 33 | 31 | Township |
| Perry | 12 | 845 | 849 | -0.12% | 1,128 | 1 | City |
| McLouth | 13 | 832 | 859 | -0.72% | 1,444 | 1 | City |
| Rural | 14 | 803 | 794 | 0.38% | 25 | 32 | Township |
| Meriden | 15 | 713 | 743 | -0.83% | 927 | 1 | City |
| Ozawkie | 16 | 620 | 635 | -0.48% | 2,088 | 0 | City |
| Nortonville | 17 | 582 | 601 | -0.68% | 1,347 | 0 | City |
| Winchester | 18 | 440 | 453 | -0.68% | 1,337 | 0 | City |
| Grantville | 19 | 230 | 206 | 1.32% | 375 | 1 | CDP |
| Williamstown | 20 | 200 | 129 | 6.95% | 1,709 | 0 | CDP |
| Perry | 21 | 108 | 104 | 0.93% | 2 | 49 | Township |
Rock Creek is the largest city in Jefferson County, with a population of 2,787.
Perry is the smallest city in Jefferson County, with a population of 108.
There are 21 cities in Jefferson County, Kansas.