13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Newton | 1 | 15,576 | 15,748 | -0.22% | 1,384 | 11.26 | City |
| Colfax | 2 | 2,268 | 2,253 | 0.13% | 886 | 2.56 | City |
| Monroe | 3 | 2,038 | 1,968 | 0.69% | 1,200 | 1.70 | City |
| Prairie City | 4 | 1,722 | 1,696 | 0.29% | 1,386 | 1.24 | City |
| Baxter | 5 | 980 | 970 | 0.2% | 1,498 | 0.65 | City |
| Sully | 6 | 888 | 880 | 0.23% | 1,526 | 0.58 | City |
| Kellogg | 7 | 592 | 601 | -0.34% | 1,596 | 0.37 | City |
| Lynnville | 8 | 384 | 381 | 0.26% | 349 | 1.10 | City |
| Mingo | 9 | 319 | 303 | 0.95% | 518 | 0.62 | City |
| Oakland Acres | 10 | 178 | 175 | 0.56% | 625 | 0.28 | City |
| Lambs Grove | 11 | 168 | 170 | 0% | 1,647 | 0.10 | City |
| Reasnor | 12 | 156 | 155 | 0% | 281 | 0.56 | City |
| Valeria | 13 | 40 | 37 | 2.56% | 816 | 0.05 | City |
Newton is the largest city in Jasper County, with a population of 15,576.
Valeria is the smallest city in Jasper County.
There are 13 cities in Jasper County, Iowa.