34 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Flagg | 1 | 13,579 | 13,343 | 0.88% | 382 | 36 | Township |
| Rochelle | 2 | 9,529 | 9,472 | 0.11% | 693 | 14 | City |
| Byron | 3 | 6,352 | 6,434 | -0.35% | 173 | 37 | Township |
| Oregon-Nashua | 4 | 4,711 | 4,819 | -0.38% | 123 | 38 | Township |
| Byron | 5 | 3,753 | 3,785 | -0.13% | 807 | 5 | City |
| Mount Morris | 6 | 3,600 | 3,704 | -0.61% | 100 | 36 | Township |
| Oregon | 7 | 3,540 | 3,630 | -0.42% | 1,837 | 2 | City |
| Scott | 8 | 3,300 | 3,297 | -0.18% | 92 | 36 | Township |
| Mount Morris | 9 | 2,764 | 2,847 | -0.5% | 1,772 | 2 | Village |
| Davis Junction | 10 | 2,545 | 2,511 | 0.24% | 606 | 4 | Village |
| Polo | 11 | 2,216 | 2,282 | -0.49% | 1,527 | 1 | City |
| Forreston | 12 | 1,927 | 1,989 | -0.62% | 53 | 36 | Township |
| Rockvale | 13 | 1,744 | 1,779 | -0.51% | 50 | 35 | Township |
| Monroe | 14 | 1,420 | 1,443 | -0.28% | 39 | 36 | Township |
| Forreston | 15 | 1,387 | 1,434 | -0.57% | 1,471 | 1 | Village |
| Leaf River | 16 | 1,056 | 1,088 | -0.66% | 29 | 36 | Township |
| Stillman Valley | 17 | 1,042 | 1,071 | -0.48% | 1,828 | 1 | Village |
| Dement | 18 | 946 | 952 | 0.21% | 27 | 35 | Township |
| Pine Rock | 19 | 924 | 944 | -0.54% | 24 | 38 | Township |
| Taylor | 20 | 911 | 925 | -0.33% | 60 | 15 | Township |
| New Milford | 21 | 809 | 802 | 0.12% | 287 | 3 | Village |
| Pine Creek | 22 | 694 | 707 | -0.43% | 17 | 40 | Township |
| White Rock | 23 | 676 | 691 | -0.44% | 19 | 36 | Township |
| Grand Detour | 24 | 643 | 656 | -0.46% | 58 | 11 | Township |
| Creston | 25 | 614 | 626 | -0.32% | 536 | 1 | Village |
| Lynnville | 26 | 565 | 579 | -0.53% | 16 | 35 | Township |
| Maryland | 27 | 500 | 510 | -0.4% | 14 | 36 | Township |
| Leaf River | 28 | 414 | 428 | -0.48% | 476 | 1 | Village |
| Monroe Center | 29 | 402 | 413 | -0.5% | 332 | 1 | Village |
| Woosung | 30 | 350 | 350 | 0% | 20 | 18 | Township |
| Brookville | 31 | 232 | 240 | -0.85% | 13 | 18 | Township |
| Eagle Point | 32 | 190 | 195 | -0.52% | 10 | 20 | Township |
| Lafayette | 33 | 148 | 150 | 0% | 8 | 17 | Township |
| Adeline | 34 | 74 | 76 | 0% | 278 | 0 | Village |
Flagg is the largest city in Ogle County, with a population of 13,579.
Adeline is the smallest city in Ogle County, with a population of 74.
There are 34 cities in Ogle County, Illinois.