| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Mount Vernon | 1 | 17,325 | 17,068 | 0.22% | 1,746 | 10 | City |
| Fredericktown | 2 | 2,658 | 2,651 | 0% | 1,340 | 2 | Village |
| Gambier | 3 | 2,248 | 2,222 | 0.67% | 2,399 | 1 | Village |
| Centerburg | 4 | 1,687 | 1,727 | -0.24% | 1,745 | 1 | Village |
| Danville | 5 | 1,021 | 1,024 | -0.39% | 1,728 | 1 | Village |
| Martinsburg | 6 | 220 | 226 | -0.9% | 1,243 | 0 | Village |
Mount Vernon is the largest city in Knox County, with a population of 17,325.
Martinsburg is the smallest city in Knox County, with a population of 220.
There are 6 cities in Knox County, Ohio.