| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Galesburg | 1 | 28,267 | 29,949 | -1.1% | 1,592 | 18 | City |
| Abingdon | 2 | 2,807 | 2,946 | -0.88% | 1,970 | 1 | City |
| Knoxville | 3 | 2,790 | 2,898 | -0.71% | 1,187 | 2 | City |
| East Galesburg | 4 | 728 | 758 | -0.82% | 533 | 1 | Village |
| Wataga | 5 | 705 | 741 | -0.98% | 850 | 1 | Village |
| Oneida | 6 | 671 | 700 | -0.89% | 879 | 1 | City |
| Yates City | 7 | 624 | 653 | -0.79% | 1,266 | 0 | Village |
| Williamsfield | 8 | 546 | 569 | -0.73% | 444 | 1 | Village |
| Altona | 9 | 445 | 465 | -0.89% | 474 | 1 | Village |
| Henderson | 10 | 252 | 262 | -0.79% | 951 | 0 | Village |
| Victoria | 11 | 249 | 262 | -1.19% | 552 | 0 | Village |
| Maquon | 12 | 209 | 221 | -0.95% | 1,290 | 0 | Village |
| Rio | 13 | 201 | 209 | -0.99% | 644 | 0 | Village |
| St. Augustine | 14 | 112 | 117 | -0.88% | 189 | 1 | Village |
Galesburg is the largest city in Knox County, with a population of 28,267.
St. Augustine is the smallest city in Knox County, with a population of 112.
There are 14 cities in Knox County, Illinois.