16 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| John Day | 1 | 1,632 | 1,673 | -0.55% | 722 | 2 | City |
| John Day | 2 | 1,632 | 1,676 | -0.55% | 722 | 2 | City |
| Prairie City | 3 | 812 | 836 | -0.61% | 819 | 1 | City |
| Prairie City | 4 | 812 | 836 | -0.61% | 819 | 1 | City |
| Canyon City | 5 | 638 | 659 | -0.78% | 453 | 1 | Town |
| Canyon City | 6 | 638 | 660 | -0.78% | 453 | 1 | Town |
| Mount Vernon | 7 | 546 | 548 | -0.18% | 799 | 1 | City |
| Mount Vernon | 8 | 546 | 549 | -0.18% | 799 | 1 | City |
| Long Creek | 9 | 167 | 171 | -0.6% | 163 | 1 | City |
| Long Creek | 10 | 167 | 171 | -0.6% | 163 | 1 | City |
| Seneca | 11 | 161 | 166 | -0.62% | 203 | 1 | City |
| Seneca | 12 | 161 | 166 | -0.62% | 203 | 1 | City |
| Dayville | 13 | 129 | 132 | -0.77% | 245 | 1 | Town |
| Dayville | 14 | 129 | 132 | -0.77% | 245 | 1 | Town |
| Monument | 15 | 111 | 111 | 0% | 218 | 1 | City |
| Monument | 16 | 111 | 111 | 0% | 218 | 1 | City |
John Day is the largest city in Grant County, with a population of 1,632.
Monument is the smallest city in Grant County, with a population of 111.
There are 16 cities in Grant County, Oregon.