19 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rock Creek | 1 | 2,793 | 2,778 | 0.22% | 52 | 54 | Township |
| Oskaloosa | 2 | 2,153 | 2,162 | -0.05% | 38 | 57 | Township |
| Delaware | 3 | 1,780 | 1,812 | -0.34% | 20 | 88 | Township |
| Union | 4 | 1,651 | 1,661 | 0.12% | 39 | 42 | Township |
| Ozawkie | 5 | 1,650 | 1,646 | 0.12% | 44 | 38 | Township |
| Kentucky | 6 | 1,553 | 1,539 | 0.32% | 43 | 36 | Township |
| Kaw | 7 | 1,410 | 1,386 | 0.36% | 44 | 32 | Township |
| Jefferson | 8 | 1,064 | 1,071 | -0.09% | 18 | 58 | Township |
| Oskaloosa | 9 | 1,060 | 1,098 | -0.56% | 1,066 | 1 | City |
| Valley Falls | 10 | 1,053 | 1,091 | -0.57% | 1,496 | 1 | City |
| Sarcoxie | 11 | 1,006 | 988 | 0.4% | 33 | 31 | Township |
| Perry | 12 | 844 | 849 | -0.12% | 1,127 | 1 | City |
| McLouth | 13 | 827 | 859 | -0.6% | 1,436 | 1 | City |
| Rural | 14 | 806 | 794 | 0.37% | 25 | 32 | Township |
| Meriden | 15 | 707 | 743 | -0.84% | 919 | 1 | City |
| Ozawkie | 16 | 617 | 635 | -0.48% | 2,077 | 0 | City |
| Nortonville | 17 | 578 | 601 | -0.69% | 1,338 | 0 | City |
| Winchester | 18 | 438 | 453 | -0.45% | 1,331 | 0 | City |
| Perry | 19 | 109 | 104 | 0.93% | 2 | 49 | Township |
Rock Creek is the largest city in Jefferson County, with a population of 2,793.
Perry is the smallest city in Jefferson County, with a population of 109.
There are 19 cities in Jefferson County, Kansas.