25 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rockford | 1 | 170,816 | 170,230 | 0.5% | 1,539 | 111 | Township |
| Rockford | 2 | 146,881 | 148,696 | -0.21% | 2,246 | 65 | City |
| Harlem | 3 | 39,795 | 39,212 | 0.65% | 1,218 | 33 | Township |
| Loves Park | 4 | 23,754 | 23,400 | 0.25% | 1,455 | 16 | City |
| Machesney Park | 5 | 22,792 | 22,933 | -0.1% | 1,797 | 13 | Village |
| Roscoe | 6 | 20,501 | 20,227 | 0.66% | 668 | 31 | Township |
| Cherry Valley | 7 | 19,497 | 19,333 | 0.59% | 643 | 30 | Township |
| Rockton | 8 | 16,345 | 16,138 | 0.65% | 451 | 36 | Township |
| Roscoe | 9 | 10,990 | 10,962 | 0.05% | 1,071 | 10 | Village |
| South Beloit | 10 | 7,983 | 7,982 | 0% | 1,299 | 6 | City |
| Rockton | 11 | 7,862 | 7,859 | 0.01% | 1,146 | 7 | Village |
| Seward | 12 | 6,757 | 6,651 | -0.09% | 193 | 35 | Township |
| Winnebago | 13 | 5,030 | 4,989 | 0.62% | 153 | 33 | Township |
| Pecatonica | 14 | 4,171 | 4,147 | 0.53% | 119 | 35 | Township |
| Owen | 15 | 3,630 | 3,600 | 0.55% | 103 | 35 | Township |
| Winnebago | 16 | 2,898 | 2,924 | -0.14% | 1,498 | 2 | Village |
| Cherry Valley | 17 | 2,886 | 2,892 | -0.03% | 343 | 8 | Village |
| Durand | 18 | 2,324 | 2,306 | 0.52% | 78 | 30 | Township |
| Pecatonica | 19 | 2,047 | 2,080 | -0.24% | 1,595 | 1 | Village |
| Durand | 20 | 1,380 | 1,389 | -0.07% | 1,502 | 1 | Village |
| Laona | 21 | 1,277 | 1,265 | 0.55% | 47 | 27 | Township |
| Burritt | 22 | 1,114 | 1,098 | 0.81% | 34 | 33 | Township |
| Shirland | 23 | 980 | 965 | 0.82% | 51 | 19 | Township |
| Seward | 24 | 850 | 844 | 0.59% | 24 | 36 | Township |
| Harrison | 25 | 612 | 609 | 0.49% | 25 | 25 | Township |
Rockford is the largest city in Winnebago County, with a population of 170,816.
Harrison is the smallest city in Winnebago County, with a population of 612.
There are 25 cities in Winnebago County, Illinois.