| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Rochelle | 1 | 9,504 | 9,473 | 0.06% | 691 | 14 | City |
| Byron | 2 | 3,770 | 3,786 | -0.19% | 811 | 5 | City |
| Oregon | 3 | 3,557 | 3,632 | -0.45% | 1,846 | 2 | City |
| Mount Morris | 4 | 2,772 | 2,847 | -0.54% | 1,777 | 2 | Village |
| Davis Junction | 5 | 2,571 | 2,510 | 0.19% | 612 | 4 | Village |
| Polo | 6 | 2,223 | 2,284 | -0.54% | 1,532 | 1 | City |
| Forreston | 7 | 1,394 | 1,433 | -0.57% | 1,478 | 1 | Village |
| Stillman Valley | 8 | 1,053 | 1,073 | -0.47% | 1,847 | 1 | Village |
| New Milford | 9 | 809 | 801 | 0.12% | 287 | 3 | Village |
| Creston | 10 | 634 | 629 | -0.47% | 553 | 1 | Village |
| Leaf River | 11 | 415 | 427 | -0.48% | 478 | 1 | Village |
| Monroe Center | 12 | 404 | 414 | -0.49% | 333 | 1 | Village |
| Adeline | 13 | 71 | 73 | -1.39% | 267 | 0 | Village |
Rochelle is the largest city in Ogle County, with a population of 9,504.
Adeline is the smallest city in Ogle County, with a population of 71.
There are 13 cities in Ogle County, Illinois.