16 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Galesburg | 1 | 28,587 | 29,944 | -0.94% | 1,610 | 17.76 | City |
| Abingdon | 2 | 2,788 | 2,945 | -1.1% | 1,956 | 1.43 | City |
| Knoxville | 3 | 2,764 | 2,891 | -0.9% | 1,176 | 2.35 | City |
| East Galesburg | 4 | 726 | 761 | -0.95% | 532 | 1.36 | Village |
| Oak Run | 5 | 704 | 468 | 1.44% | 165 | 4.28 | CDP |
| Wataga | 6 | 700 | 740 | -1.13% | 844 | 0.83 | Village |
| Oneida | 7 | 661 | 696 | -1.05% | 866 | 0.76 | City |
| Yates City | 8 | 610 | 642 | -0.97% | 1,237 | 0.49 | Village |
| Williamsfield | 9 | 540 | 569 | -1.1% | 439 | 1.23 | Village |
| Altona | 10 | 437 | 462 | -1.13% | 466 | 0.94 | Village |
| Henderson | 11 | 251 | 263 | -0.79% | 947 | 0.27 | Village |
| Victoria | 12 | 249 | 268 | -1.58% | 552 | 0.45 | Village |
| Maquon | 13 | 210 | 222 | -0.94% | 1,296 | 0.16 | Village |
| Rio | 14 | 200 | 209 | -0.99% | 641 | 0.31 | Village |
| St. Augustine | 15 | 110 | 117 | -0.9% | 185 | 0.59 | Village |
| Gilson | 16 | 104 | 194 | -5.46% | 314 | 0.33 | CDP |
Galesburg is the largest city in Knox County, with a population of 28,587.
Gilson is the smallest city in Knox County.
There are 16 cities in Knox County, Illinois.