| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Tarkio | 1 | 1,468 | 1,511 | -0.68% | 1,058 | 1 | City |
| Rock Port | 2 | 1,238 | 1,276 | -0.64% | 447 | 3 | City |
| Fairfax | 3 | 622 | 646 | -0.8% | 1,338 | 0 | City |
| Westboro | 4 | 112 | 117 | -0.88% | 443 | 0 | City |
| Big Lake | 5 | 71 | 68 | 0% | 43 | 2 | Village |
| Watson | 6 | 57 | 59 | -1.72% | 523 | 0 | Village |
| Fortescue | 7 | 21 | 21 | 0% | 273 | 0 | Town |
| Bigelow | 8 | 4 | 4 | 0% | 42 | 0 | Village |
| Corning | 9 | 0 | 0 | 0 | 0 | Town |
Tarkio is the largest city in Atchison County, with a population of 1,468.
Corning is the smallest city in Atchison County, with a population of 0.
There are 9 cities in Atchison County, Missouri.