10 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sterling | 1 | 14,384 | 14,837 | -0.52% | 2,419 | 6 | City |
| Rock Falls | 2 | 8,535 | 8,771 | -0.45% | 2,143 | 4 | City |
| Morrison | 3 | 3,947 | 4,070 | -0.5% | 1,568 | 3 | City |
| Fulton | 4 | 3,548 | 3,647 | -0.45% | 1,518 | 2 | City |
| Prophetstown | 5 | 1,890 | 1,938 | -0.42% | 1,412 | 1 | City |
| Erie | 6 | 1,479 | 1,515 | -0.4% | 1,072 | 1 | Village |
| Albany | 7 | 846 | 861 | -0.24% | 790 | 1 | Village |
| Tampico | 8 | 666 | 692 | -0.6% | 1,690 | 0 | Village |
| Lyndon | 9 | 526 | 535 | -0.19% | 695 | 1 | Village |
| Deer Grove | 10 | 40 | 36 | 2.56% | 97 | 0 | Village |
Sterling is the largest city in Whiteside County, with a population of 14,384.
Deer Grove is the smallest city in Whiteside County, with a population of 40.
There are 10 cities in Whiteside County, Illinois.