| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| John Day | 1 | 1,626 | 1,674 | -0.49% | 719 | 2 | City |
| Prairie City | 2 | 814 | 842 | -0.61% | 821 | 1 | City |
| Canyon City | 3 | 640 | 663 | -0.62% | 455 | 1 | Town |
| Mount Vernon | 4 | 544 | 549 | -0.18% | 796 | 1 | City |
| Long Creek | 5 | 164 | 170 | -1.2% | 160 | 1 | City |
| Seneca | 6 | 158 | 166 | -1.25% | 199 | 1 | City |
| Dayville | 7 | 129 | 133 | -0.77% | 245 | 1 | Town |
| Monument | 8 | 111 | 114 | -0.89% | 218 | 1 | City |
John Day is the largest city in Grant County, with a population of 1,626.
Monument is the smallest city in Grant County, with a population of 111.
There are 8 cities in Grant County, Oregon.