25 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Arnold | 1 | 21,196 | 20,853 | 0.33% | 1,839 | 12 | City |
| Festus | 2 | 13,924 | 12,721 | 1.76% | 2,358 | 6 | City |
| Murphy | 3 | 8,361 | 8,373 | -0.26% | 2,164 | 4 | CDP |
| De Soto | 4 | 6,525 | 6,445 | 0.25% | 1,489 | 4 | City |
| Barnhart | 5 | 6,129 | 6,676 | 0.48% | 1,237 | 5 | CDP |
| Pevely | 6 | 6,073 | 6,050 | 0.08% | 1,201 | 5 | City |
| Herculaneum | 7 | 5,599 | 4,713 | 3.26% | 1,347 | 4 | City |
| Imperial | 8 | 5,554 | 4,947 | 1.02% | 1,060 | 5 | CDP |
| High Ridge | 9 | 4,737 | 4,257 | 0.59% | 1,256 | 4 | CDP |
| Crystal City | 10 | 4,705 | 4,734 | -0.13% | 1,042 | 5 | City |
| Hillsboro | 11 | 3,509 | 3,491 | 0.11% | 913 | 4 | City |
| Byrnes Mill | 12 | 3,191 | 3,176 | 0.09% | 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 | 712 | 719 | -0.14% | 1,367 | 1 | City |
| Briarwood Estates | 20 | 349 | 255 | 7.06% | 513 | 1 | CDP |
| Cedar Hill Lakes | 21 | 199 | 204 | -0.5% | 917 | 0 | Village |
| Scotsdale | 22 | 199 | 193 | 0.51% | 343 | 1 | Town |
| Parkdale | 23 | 154 | 156 | 0% | 1,203 | 0 | Village |
| Kimmswick | 24 | 134 | 136 | 0% | 573 | 0 | City |
| Peaceful Village | 25 | 98 | 95 | 1.03% | 500 | 0 | Village |
Arnold is the largest city in Jefferson County, with a population of 21,196.
Peaceful Village is the smallest city in Jefferson County, with a population of 98.
There are 25 cities in Jefferson County, Missouri.