There are 22 cities in Boone County, Illinois.
Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Population | 2020 Population | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rockford | 1 | 145,270 | 148,670 | -0.58% | 2,232 | 65.1 | City |
| Belvidere | 2 | 25,301 | 25,283 | 0.02% | 2,022 | 12.5 | City |
| Loves Park | 3 | 23,312 | 23,404 | -0.1% | 1,428 | 16.3 | City |
| Machesney Park | 4 | 22,529 | 22,932 | -0.45% | 1,776 | 12.7 | Village |
| Roscoe | 5 | 10,805 | 10,957 | -0.35% | 1,053 | 10.3 | Village |
| Harvard | 6 | 9,323 | 9,455 | -0.35% | 1,113 | 8.4 | City |
| South Beloit | 7 | 7,865 | 7,975 | -0.36% | 1,280 | 6.1 | City |
| Rockton | 8 | 7,740 | 7,851 | -0.36% | 1,128 | 6.9 | Village |
| Candlewick Lake | 9 | 5,927 | 5,351 | 7.7% | 3,206 | 1.8 | CDP |
| Genoa | 10 | 5,480 | 5,307 | 0.79% | 2,111 | 2.6 | City |
| Poplar Grove | 11 | 5,153 | 5,056 | 0.47% | 654 | 7.9 | Village |
| Cherry Valley | 12 | 2,853 | 2,896 | -0.38% | 339 | 8.4 | Village |
| Kirkland | 13 | 1,608 | 1,648 | -0.62% | 1,295 | 1.2 | Village |
| Capron | 14 | 1,397 | 1,388 | 0.14% | 1,810 | 0.8 | Village |
| Kingston | 15 | 1,083 | 1,106 | -0.55% | 1,101 | 1.0 | Village |
| Timberlane | 16 | 902 | 904 | -0.11% | 517 | 1.7 | Village |
| Argyle | 17 | 672 | 353 | 7.69% | 766 | 0.9 | CDP |
| Chemung | 18 | 399 | 738 | 1.79% | 1,420 | 0.3 | CDP |
| Garden Prairie | 19 | 383 | 265 | 7.89% | 600 | 0.6 | CDP |
| Lawrence | 20 | 234 | 150 | 7.34% | 636 | 0.4 | CDP |
| Alden | 21 | 196 | 167 | 7.69% | 1,556 | 0.1 | CDP |
| Caledonia | 22 | 179 | 182 | -0.56% | 173 | 1.0 | Village |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Rockford is the largest city in Boone County.
Caledonia is the smallest city in Boone County.
There are 22 cities in Boone County, Illinois.