14 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Galesburg | 1 | 28,962 | 29,942 | -0.56% | 1,631 | 18 | City |
| Abingdon | 2 | 2,832 | 2,949 | -0.67% | 1,987 | 1 | City |
| Knoxville | 3 | 2,813 | 2,894 | -0.46% | 1,197 | 2 | City |
| East Galesburg | 4 | 735 | 761 | -0.54% | 538 | 1 | Village |
| Wataga | 5 | 714 | 741 | -0.56% | 861 | 1 | Village |
| Oneida | 6 | 673 | 696 | -0.59% | 882 | 1 | City |
| Yates City | 7 | 630 | 651 | -0.47% | 1,278 | 0 | Village |
| Williamsfield | 8 | 550 | 570 | -0.54% | 447 | 1 | Village |
| Altona | 9 | 445 | 462 | -0.67% | 474 | 1 | Village |
| Victoria | 10 | 255 | 266 | -0.78% | 565 | 0 | Village |
| Henderson | 11 | 254 | 262 | -0.39% | 958 | 0 | Village |
| Maquon | 12 | 211 | 222 | -0.94% | 1,302 | 0 | Village |
| Rio | 13 | 203 | 209 | -0.49% | 651 | 0 | Village |
| St. Augustine | 14 | 112 | 117 | -0.88% | 189 | 1 | Village |
Galesburg is the largest city in Knox County, with a population of 28,962.
St. Augustine is the smallest city in Knox County, with a population of 112.
There are 14 cities in Knox County, Illinois.