10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Tarkio | 1 | 1,422 | 1,512 | -1.25% | 1,025 | 1 | City |
| Rock Port | 2 | 1,197 | 1,272 | -1.24% | 432 | 3 | City |
| Fairfax | 3 | 603 | 648 | -1.47% | 1,297 | 0 | City |
| Westboro | 4 | 109 | 116 | -0.91% | 431 | 0 | City |
| Big Lake | 5 | 74 | 71 | 1.37% | 45 | 2 | Village |
| Watson | 6 | 54 | 58 | -1.82% | 495 | 0 | Village |
| Fortescue | 7 | 20 | 20 | 0% | 260 | 0 | Town |
| Quitman | 8 | 19 | 10 | 5.56% | 121 | 0 | CDP |
| Bigelow | 9 | 6 | 6 | 0% | 63 | 0 | Village |
| Corning | 10 | 0 | 0 | 0.00 | 0 | Town |
Tarkio is the largest city in Atchison County, with a population of 1,422.
Corning is the smallest city in Atchison County, with a population of 0.
There are 10 cities in Atchison County, Missouri.