| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rockland | 1 | 7,240 | 6,952 | 1.37% | 563 | 13 | City |
| Camden | 2 | 5,209 | 5,238 | 0.1% | 286 | 18 | Town |
| Warren | 3 | 5,136 | 4,886 | 0.73% | 111 | 46 | Town |
| Rockport | 4 | 3,616 | 3,639 | -0.33% | 167 | 22 | Town |
| Thomaston | 5 | 2,753 | 2,736 | 0.07% | 252 | 11 | Town |
| St. George | 6 | 2,596 | 2,597 | 0.04% | 104 | 25 | Town |
| Union | 7 | 2,460 | 2,376 | 0.65% | 77 | 32 | Town |
| Hope | 8 | 1,742 | 1,706 | 0.29% | 79 | 22 | Town |
| Washington | 9 | 1,556 | 1,595 | -0.38% | 41 | 38 | Town |
| South Thomaston | 10 | 1,517 | 1,512 | -0.2% | 133 | 11 | Town |
| Owls Head | 11 | 1,488 | 1,506 | -0.4% | 168 | 9 | Town |
| Appleton | 12 | 1,483 | 1,417 | 0.95% | 45 | 33 | Town |
| Cushing | 13 | 1,478 | 1,504 | -0.27% | 77 | 19 | Town |
| Vinalhaven | 14 | 1,247 | 1,289 | -0.56% | 53 | 23 | Town |
| Friendship | 15 | 1,166 | 1,143 | 0.6% | 83 | 14 | Town |
| North Haven | 16 | 438 | 420 | 1.39% | 38 | 12 | Town |
| Isle au Haut | 17 | 84 | 85 | 0% | 7.0 | 13 | Town |
| Matinicus Isle | 18 | 50 | 51 | 0% | 21 | 2 | Plantation |
Rockland is the largest city in Knox County, with a population of 7,240.
Matinicus Isle is the smallest city in Knox County, with a population of 50.
There are 18 cities in Knox County, Maine.