13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Newton | 1 | 15,698 | 15,750 | -0.07% | 1,395 | 11 | City |
| Colfax | 2 | 2,317 | 2,254 | 0.52% | 905 | 3 | City |
| Monroe | 3 | 2,034 | 1,968 | 0.64% | 1,198 | 2 | City |
| Prairie City | 4 | 1,728 | 1,698 | 0.35% | 1,391 | 1 | City |
| Baxter | 5 | 986 | 971 | 0.31% | 1,508 | 1 | City |
| Sully | 6 | 893 | 880 | 0.22% | 1,534 | 1 | City |
| Kellogg | 7 | 596 | 601 | -0.17% | 1,606 | 0 | City |
| Lynnville | 8 | 382 | 382 | 0% | 348 | 1 | City |
| Mingo | 9 | 316 | 303 | 0.64% | 513 | 1 | City |
| Oakland Acres | 10 | 178 | 175 | 0% | 625 | 0 | City |
| Lambs Grove | 11 | 174 | 174 | 0% | 1,706 | 0 | City |
| Reasnor | 12 | 157 | 155 | 0% | 283 | 1 | City |
| Valeria | 13 | 41 | 39 | 0% | 837 | 0 | City |
Newton is the largest city in Jasper County, with a population of 15,698.
Valeria is the smallest city in Jasper County, with a population of 41.
There are 13 cities in Jasper County, Iowa.