9 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Joseph | 1 | 70,834 | 72,153 | -0.37% | 1,609 | 44 | City |
| Agency | 2 | 649 | 667 | -0.61% | 176 | 4 | Village |
| De Kalb | 3 | 241 | 230 | 0.84% | 945 | 0 | Town |
| Faucett | 4 | 241 | 209 | 7.11% | 244 | 1 | CDP |
| Easton | 5 | 226 | 226 | 0% | 384 | 1 | City |
| Rushville | 6 | 217 | 222 | -0.46% | 1,096 | 0 | Village |
| Ridgely | 7 | 103 | 96 | 0.98% | 75 | 1 | Village |
| Lewis Clark Village | 8 | 91 | 94 | -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 70,834.
New Market is the smallest city in Buchanan County, with a population of 82.
There are 9 cities in Buchanan County, Missouri.