21 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Moline | 1 | 41,343 | 42,897 | -0.75% | 2,468 | 16.75 | City |
| Rock Island | 2 | 35,540 | 37,019 | -0.83% | 2,107 | 16.87 | City |
| East Moline | 3 | 20,462 | 21,322 | -0.83% | 1,402 | 14.60 | City |
| Silvis | 4 | 7,832 | 7,991 | -0.41% | 1,828 | 4.29 | City |
| Milan | 5 | 4,888 | 5,088 | -0.81% | 781 | 6.25 | Village |
| Coal Valley | 6 | 3,784 | 3,864 | -0.42% | 1,195 | 3.17 | Village |
| Carbon Cliff | 7 | 1,759 | 1,841 | -0.9% | 840 | 2.10 | Village |
| Hampton | 8 | 1,714 | 1,774 | -0.69% | 1,173 | 1.46 | Village |
| Port Byron | 9 | 1,602 | 1,664 | -0.74% | 660 | 2.43 | Village |
| Andalusia | 10 | 1,144 | 1,181 | -0.61% | 974 | 1.18 | Village |
| Rapids City | 11 | 924 | 958 | -0.75% | 568 | 1.63 | Village |
| Cordova | 12 | 644 | 674 | -0.92% | 1,122 | 0.57 | Village |
| Campbell's Island | 13 | 521 | 343 | 7.2% | 1,148 | 0.45 | CDP |
| Edgington | 14 | 519 | 195 | 7.23% | 513 | 1.01 | CDP |
| Reynolds | 15 | 474 | 499 | -1.04% | 1,288 | 0.37 | Village |
| Rock Island Arsenal | 16 | 431 | 353 | 4.36% | 274 | 1.57 | CDP |
| Hillsdale | 17 | 403 | 413 | -0.49% | 622 | 0.65 | Village |
| Taylor Ridge | 18 | 164 | 142 | 7.19% | 106 | 1.55 | CDP |
| Barstow | 19 | 81 | 73 | 6.58% | 764 | 0.11 | CDP |
| Joslin | 20 | 74 | 30 | 7.25% | 16 | 4.64 | CDP |
| Illinois City | 21 | 46 | 58 | 6.98% | 101 | 0.46 | CDP |
Moline is the largest city in Rock Island County, with a population of 41,343.
Illinois City is the smallest city in Rock Island County.
There are 21 cities in Rock Island County, Illinois.