7 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| St. Joseph | 1 | 70,570 | 72,153 | -0.37% | 1,603 | 44 | City |
| Agency | 2 | 646 | 667 | -0.46% | 175 | 4 | Village |
| De Kalb | 3 | 243 | 230 | 0.83% | 953 | 0 | Town |
| Easton | 4 | 226 | 226 | 0% | 384 | 1 | City |
| Rushville | 5 | 216 | 222 | -0.46% | 1,091 | 0 | Village |
| Ridgely | 6 | 105 | 96 | 1.94% | 76 | 1 | Village |
| Lewis and Clark Village | 7 | 91 | 94 | 0% | 149 | 1 | Town |
St. Joseph is the largest city in Buchanan County, with a population of 70,570.
Lewis and Clark Village is the smallest city in Buchanan County, with a population of 91.
There are 7 cities in Buchanan County, Missouri.