9 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Tarkio | 1 | 1,447 | 1,515 | -0.75% | 1,043 | 1 | City |
| Rock Port | 2 | 1,219 | 1,275 | -0.73% | 440 | 3 | City |
| Fairfax | 3 | 611 | 647 | -0.97% | 1,314 | 0 | City |
| Westboro | 4 | 110 | 115 | -0.9% | 435 | 0 | City |
| Big Lake | 5 | 73 | 70 | 1.39% | 44 | 2 | Village |
| Watson | 6 | 55 | 57 | 0% | 505 | 0 | Village |
| Fortescue | 7 | 21 | 21 | 0% | 273 | 0 | Town |
| Bigelow | 8 | 6 | 6 | 0% | 63 | 0 | Village |
| Corning | 9 | 0 | 0 | 0.00 | 0 | Town |
Tarkio is the largest city in Atchison County, with a population of 1,447.
Corning is the smallest city in Atchison County, with a population of 0.
There are 9 cities in Atchison County, Missouri.