30 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sterling | 1 | 17,013 | 17,317 | 0.08% | 728 | 23 | Township |
| Sterling | 2 | 14,384 | 14,837 | -0.52% | 2,419 | 6 | City |
| Coloma | 3 | 10,398 | 10,560 | 0.07% | 1,036 | 10 | Township |
| Rock Falls | 4 | 8,535 | 8,771 | -0.45% | 2,143 | 4 | City |
| Mount Pleasant | 5 | 4,697 | 4,778 | 0.09% | 131 | 36 | Township |
| Fulton | 6 | 4,289 | 4,351 | 0.14% | 247 | 17 | Township |
| Morrison | 7 | 3,947 | 4,070 | -0.5% | 1,568 | 3 | City |
| Fulton | 8 | 3,548 | 3,647 | -0.45% | 1,518 | 2 | City |
| Prophetstown | 9 | 2,456 | 2,488 | 0.16% | 51 | 48 | Township |
| Montmorency | 10 | 2,425 | 2,439 | 0.29% | 68 | 36 | Township |
| Hopkins | 11 | 1,990 | 2,009 | 0.2% | 56 | 36 | Township |
| Prophetstown | 12 | 1,890 | 1,938 | -0.42% | 1,412 | 1 | City |
| Erie | 13 | 1,861 | 1,882 | 0.22% | 78 | 24 | Township |
| Erie | 14 | 1,479 | 1,515 | -0.4% | 1,072 | 1 | Village |
| Union Grove | 15 | 1,188 | 1,197 | 0.17% | 34 | 35 | Township |
| Albany | 16 | 1,008 | 1,017 | 0.1% | 81 | 12 | Township |
| Garden Plain | 17 | 978 | 986 | 0.2% | 32 | 31 | Township |
| Tampico | 18 | 975 | 996 | 0% | 27 | 36 | Township |
| Lyndon | 19 | 917 | 914 | 0.66% | 34 | 27 | Township |
| Albany | 20 | 846 | 861 | -0.24% | 790 | 1 | Village |
| Jordan | 21 | 845 | 853 | 0.24% | 24 | 36 | Township |
| Genesee | 22 | 703 | 712 | 0.14% | 20 | 35 | Township |
| Tampico | 23 | 666 | 692 | -0.6% | 1,690 | 0 | Village |
| Fenton | 24 | 564 | 564 | 0.53% | 16 | 35 | Township |
| Ustick | 25 | 536 | 542 | 0.19% | 15 | 35 | Township |
| Lyndon | 26 | 526 | 535 | -0.19% | 695 | 1 | Village |
| Portland | 27 | 429 | 433 | 0.23% | 12 | 35 | Township |
| Clyde | 28 | 398 | 399 | 0.25% | 11 | 36 | Township |
| Hahnaman | 29 | 355 | 350 | 0.85% | 10 | 36 | Township |
| Deer Grove | 30 | 40 | 36 | 2.56% | 97 | 0 | Village |
Sterling is the largest city in Whiteside County, with a population of 17,013.
Deer Grove is the smallest city in Whiteside County, with a population of 40.
There are 30 cities in Whiteside County, Illinois.