| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Sterling | 1 | 14,306 | 14,839 | -0.61% | 2,406 | 6 | City |
| Rock Falls | 2 | 8,472 | 8,770 | -0.58% | 2,127 | 4 | City |
| Morrison | 3 | 3,921 | 4,066 | -0.61% | 1,557 | 3 | City |
| Fulton | 4 | 3,519 | 3,642 | -0.59% | 1,505 | 2 | City |
| Prophetstown | 5 | 1,876 | 1,941 | -0.58% | 1,401 | 1 | City |
| Erie | 6 | 1,475 | 1,517 | -0.61% | 1,069 | 1 | Village |
| Albany | 7 | 834 | 856 | -0.48% | 779 | 1 | Village |
| Tampico | 8 | 663 | 691 | -0.75% | 1,683 | 0 | Village |
| Lyndon | 9 | 523 | 535 | -0.57% | 691 | 1 | Village |
| Deer Grove | 10 | 39 | 36 | 0% | 95 | 0 | Village |
Sterling is the largest city in Whiteside County, with a population of 14,306.
Deer Grove is the smallest city in Whiteside County, with a population of 39.
There are 10 cities in Whiteside County, Illinois.