9 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Joseph | 1 | 69,627 | 72,144 | -0.72% | 1,581 | 44 | City |
| Agency | 2 | 636 | 668 | -0.93% | 173 | 4 | Village |
| Faucett | 3 | 241 | 209 | 7.11% | 244 | 1 | CDP |
| De Kalb | 4 | 239 | 233 | 0.42% | 937 | 0 | Town |
| Easton | 5 | 222 | 226 | -0.45% | 377 | 1 | City |
| Rushville | 6 | 213 | 223 | -0.93% | 1,076 | 0 | Village |
| Ridgely | 7 | 108 | 98 | 1.89% | 78 | 1 | Village |
| Lewis Clark Village | 8 | 91 | 95 | -1.09% | 149 | 1 | Town |
| New Market | 9 | 82 | 41 | 6.49% | 429 | 0 | CDP |
St. Joseph is the largest city in Buchanan County, with a population of 69,627.
New Market is the smallest city in Buchanan County, with a population of 82.
There are 9 cities in Buchanan County, Missouri.