8 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| John Day | 1 | 1,654 | 1,666 | -0.12% | 732 | 2.26 | City |
| Prairie City | 2 | 833 | 840 | -0.12% | 840 | 0.99 | City |
| Canyon City | 3 | 650 | 660 | -0.31% | 462 | 1.41 | Town |
| Mount Vernon | 4 | 556 | 550 | 0.18% | 814 | 0.68 | City |
| Long Creek | 5 | 171 | 171 | 0% | 167 | 1.02 | City |
| Seneca | 6 | 162 | 166 | -0.61% | 204 | 0.80 | City |
| Dayville | 7 | 132 | 132 | 0% | 251 | 0.53 | Town |
| Monument | 8 | 116 | 115 | 0% | 228 | 0.51 | City |
John Day is the largest city in Grant County, with a population of 1,654.
Monument is the smallest city in Grant County.
There are 8 cities in Grant County, Oregon.