34 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Flagg | 1 | 13,461 | 13,343 | 0.88% | 379 | 36 | Township |
| Rochelle | 2 | 9,519 | 9,472 | 0.09% | 692 | 14 | City |
| Byron | 3 | 6,374 | 6,434 | -0.34% | 174 | 37 | Township |
| Oregon-Nashua | 4 | 4,729 | 4,819 | -0.38% | 123 | 38 | Township |
| Byron | 5 | 3,758 | 3,785 | -0.16% | 808 | 5 | City |
| Mount Morris | 6 | 3,622 | 3,704 | -0.6% | 100 | 36 | Township |
| Oregon | 7 | 3,555 | 3,630 | -0.42% | 1,845 | 2 | City |
| Scott | 8 | 3,306 | 3,297 | -0.18% | 92 | 36 | Township |
| Mount Morris | 9 | 2,778 | 2,847 | -0.5% | 1,781 | 2 | Village |
| Davis Junction | 10 | 2,539 | 2,511 | 0.2% | 605 | 4 | Village |
| Polo | 11 | 2,227 | 2,282 | -0.49% | 1,535 | 1 | City |
| Forreston | 12 | 1,939 | 1,989 | -0.62% | 53 | 36 | Township |
| Rockvale | 13 | 1,753 | 1,779 | -0.51% | 50 | 35 | Township |
| Monroe | 14 | 1,424 | 1,443 | -0.28% | 39 | 36 | Township |
| Forreston | 15 | 1,395 | 1,434 | -0.57% | 1,479 | 1 | Village |
| Leaf River | 16 | 1,063 | 1,088 | -0.65% | 30 | 36 | Township |
| Stillman Valley | 17 | 1,047 | 1,071 | -0.48% | 1,837 | 1 | Village |
| Dement | 18 | 944 | 952 | 0.21% | 27 | 35 | Township |
| Pine Rock | 19 | 929 | 944 | -0.54% | 24 | 38 | Township |
| Taylor | 20 | 914 | 925 | -0.33% | 60 | 15 | Township |
| New Milford | 21 | 808 | 802 | 0.12% | 287 | 3 | Village |
| Pine Creek | 22 | 697 | 707 | -0.43% | 18 | 40 | Township |
| White Rock | 23 | 679 | 691 | -0.44% | 19 | 36 | Township |
| Grand Detour | 24 | 646 | 656 | -0.46% | 59 | 11 | Township |
| Creston | 25 | 616 | 626 | -0.32% | 538 | 1 | Village |
| Lynnville | 26 | 568 | 579 | -0.53% | 16 | 35 | Township |
| Maryland | 27 | 502 | 510 | -0.4% | 14 | 36 | Township |
| Leaf River | 28 | 416 | 428 | -0.72% | 479 | 1 | Village |
| Monroe Center | 29 | 404 | 413 | -0.49% | 333 | 1 | Village |
| Woosung | 30 | 350 | 350 | 0% | 20 | 18 | Township |
| Brookville | 31 | 234 | 240 | -0.85% | 13 | 18 | Township |
| Eagle Point | 32 | 191 | 195 | -0.52% | 10 | 20 | Township |
| Lafayette | 33 | 148 | 150 | 0% | 8 | 17 | Township |
| Adeline | 34 | 74 | 76 | -1.33% | 278 | 0 | Village |
Flagg is the largest city in Ogle County, with a population of 13,461.
Adeline is the smallest city in Ogle County, with a population of 74.
There are 34 cities in Ogle County, Illinois.