34 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Galesburg City | 1 | 29,318 | 29,942 | 0.1% | 1,651 | 18 | Township |
| Galesburg | 2 | 29,125 | 29,942 | -0.56% | 1,640 | 18 | City |
| Knox | 3 | 4,850 | 4,928 | 0.21% | 137 | 35 | Township |
| Cedar | 4 | 2,984 | 3,055 | 0.13% | 83 | 36 | Township |
| Abingdon | 5 | 2,851 | 2,949 | -0.7% | 2,001 | 1 | City |
| Knoxville | 6 | 2,826 | 2,894 | -0.49% | 1,203 | 2 | City |
| Indian Point | 7 | 1,405 | 1,445 | -0.07% | 39 | 36 | Township |
| Henderson | 8 | 1,116 | 1,139 | 0.18% | 33 | 34 | Township |
| Persifer | 9 | 1,066 | 1,084 | 0.28% | 31 | 35 | Township |
| Ontario | 10 | 897 | 917 | 0.11% | 25 | 36 | Township |
| Truro | 11 | 835 | 855 | 0% | 23 | 36 | Township |
| East Galesburg | 12 | 739 | 761 | -0.67% | 541 | 1 | Village |
| Wataga | 13 | 718 | 741 | -0.69% | 866 | 1 | Village |
| Oak Run | 14 | 704 | 468 | 1.44% | 165 | 4 | CDP |
| Oneida | 15 | 677 | 696 | -0.59% | 887 | 1 | City |
| Walnut Grove | 16 | 660 | 677 | 0% | 19 | 36 | Township |
| Yates City | 17 | 633 | 651 | -0.63% | 1,284 | 0 | Village |
| Williamsfield | 18 | 553 | 570 | -0.72% | 449 | 1 | Village |
| Orange | 19 | 513 | 526 | -0.19% | 14 | 36 | Township |
| Rio | 20 | 504 | 515 | 0.2% | 14 | 36 | Township |
| Maquon | 21 | 452 | 463 | 0% | 13 | 36 | Township |
| Altona | 22 | 448 | 462 | -0.67% | 478 | 1 | Village |
| Galesburg | 23 | 385 | 389 | 0.26% | 18 | 21 | Township |
| Copley | 24 | 384 | 391 | 0.52% | 11 | 35 | Township |
| Victoria | 25 | 363 | 370 | 0.28% | 10 | 35 | Township |
| Haw Creek | 26 | 350 | 358 | 0.29% | 10 | 36 | Township |
| Lynn | 27 | 261 | 268 | 0% | 7 | 35 | Township |
| Victoria | 28 | 257 | 266 | -0.77% | 570 | 0 | Village |
| Henderson | 29 | 255 | 262 | -0.78% | 962 | 0 | Village |
| Elba | 30 | 248 | 257 | -0.8% | 7 | 36 | Township |
| Maquon | 31 | 213 | 222 | -0.93% | 1,315 | 0 | Village |
| Rio | 32 | 204 | 209 | -0.49% | 654 | 0 | Village |
| St. Augustine | 33 | 113 | 117 | -0.88% | 191 | 1 | Village |
| Gilson | 34 | 104 | 194 | -5.45% | 314 | 0 | CDP |
Galesburg City is the largest city in Knox County, with a population of 29,318.
Gilson is the smallest city in Knox County, with a population of 104.
There are 34 cities in Knox County, Illinois.