Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)
City | Rank | 2024 Pop. | 2020 Pop. | Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Moline | 1 | 41,654 | 42,897 | -0.74% | 2,486 | 16.8 | City |
| Rock Island | 2 | 35,836 | 37,019 | -0.82% | 2,124 | 16.9 | City |
| East Moline | 3 | 20,634 | 21,322 | -0.83% | 1,414 | 14.6 | City |
| Silvis | 4 | 7,864 | 7,991 | -0.4% | 1,835 | 4.3 | City |
| Milan | 5 | 4,928 | 5,088 | -0.8% | 788 | 6.3 | Village |
| Coal Valley | 6 | 3,800 | 3,864 | -0.42% | 1,200 | 3.2 | Village |
| Carbon Cliff | 7 | 1,775 | 1,841 | -0.95% | 847 | 2.1 | Village |
| Hampton | 8 | 1,726 | 1,774 | -0.69% | 1,181 | 1.5 | Village |
| Port Byron | 9 | 1,614 | 1,664 | -0.8% | 665 | 2.4 | Village |
| Andalusia | 10 | 1,151 | 1,181 | -0.69% | 980 | 1.2 | Village |
| Rapids City | 11 | 931 | 958 | -0.75% | 573 | 1.6 | Village |
| Cordova | 12 | 650 | 674 | -0.92% | 1,132 | 0.6 | Village |
| Campbell's Island | 13 | 486 | 343 | 7.52% | 1,070 | 0.5 | CDP |
| Edgington | 14 | 484 | 195 | 7.56% | 478 | 1.0 | CDP |
| Reynolds | 15 | 479 | 499 | -1.03% | 1,302 | 0.4 | Village |
| Rock Island Arsenal | 16 | 413 | 353 | 4.82% | 263 | 1.6 | CDP |
| Hillsdale | 17 | 405 | 413 | -0.49% | 625 | 0.6 | Village |
| Taylor Ridge | 18 | 153 | 142 | 7.75% | 99 | 1.6 | CDP |
| Barstow | 19 | 76 | 73 | 8.57% | 717 | 0.1 | CDP |
| Joslin | 20 | 69 | 30 | 7.81% | 15 | 4.6 | CDP |
| Illinois City | 21 | 43 | 58 | 7.5% | 94 | 0.5 | CDP |
Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.
Moline is the largest city in Rock Island County.
Illinois City is the smallest city in Rock Island County.
There are 21 cities in Rock Island County, Illinois.