25 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Arnold | 1 | 21,068 | 20,908 | 0.15% | 1,828 | 12 | City |
| Festus | 2 | 13,982 | 12,722 | 1.84% | 2,368 | 6 | City |
| Murphy | 3 | 8,361 | 8,373 | -0.26% | 2,164 | 4 | CDP |
| De Soto | 4 | 6,517 | 6,447 | 0.22% | 1,487 | 4 | City |
| Barnhart | 5 | 6,129 | 6,676 | 0.48% | 1,237 | 5 | CDP |
| Pevely | 6 | 6,117 | 6,044 | 0.23% | 1,209 | 5 | City |
| Imperial | 7 | 5,554 | 4,947 | 1.02% | 1,060 | 5 | CDP |
| Herculaneum | 8 | 5,472 | 4,714 | 2.84% | 1,316 | 4 | City |
| High Ridge | 9 | 4,737 | 4,257 | 0.59% | 1,256 | 4 | CDP |
| Crystal City | 10 | 4,695 | 4,735 | -0.17% | 1,040 | 5 | City |
| Hillsboro | 11 | 3,489 | 3,489 | 0% | 908 | 4 | City |
| Byrnes Mill | 12 | 3,191 | 3,179 | 0.06% | 621 | 5 | City |
| Terre Lac | 13 | 3,054 | 2,382 | 7.16% | 437 | 7 | CDP |
| Raintree Plantation | 14 | 2,288 | 1,980 | 7.17% | 1,172 | 2 | CDP |
| Summer Set | 15 | 1,460 | 1,030 | 7.12% | 1,601 | 1 | CDP |
| Cedar Hill | 16 | 1,386 | 1,625 | -1.56% | 604 | 2 | CDP |
| Horine | 17 | 976 | 1,090 | 1.04% | 1,371 | 1 | CDP |
| Lake Timberline | 18 | 799 | 548 | 7.1% | 336 | 2 | CDP |
| Olympian Village | 19 | 710 | 719 | -0.28% | 1,363 | 1 | City |
| Briarwood Estates | 20 | 349 | 255 | 7.06% | 513 | 1 | CDP |
| Cedar Hill Lakes | 21 | 200 | 205 | -0.5% | 922 | 0 | Village |
| Scotsdale | 22 | 196 | 193 | 0% | 338 | 1 | Town |
| Parkdale | 23 | 154 | 156 | -0.65% | 1,203 | 0 | Village |
| Kimmswick | 24 | 130 | 135 | -0.76% | 556 | 0 | City |
| Peaceful Village | 25 | 96 | 93 | 0% | 490 | 0 | Village |
Arnold is the largest city in Jefferson County, with a population of 21,068.
Peaceful Village is the smallest city in Jefferson County, with a population of 96.
There are 25 cities in Jefferson County, Missouri.