There are 29 cities in Mercer County, Illinois.
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 | State | 2024 Population | 2020 Census | Annual Change | Density (mi²) | Area (mi²) |
|---|---|---|---|---|---|---|---|
| Moline | 1 | Illinois | 41,654 | 42,897 | -0.74% | 2,486 | 16.75 |
| Rock Island | 2 | Illinois | 35,836 | 37,019 | -0.82% | 2,124 | 16.87 |
| Milan | 3 | Illinois | 4,928 | 5,088 | -0.8% | 788 | 6.25 |
| Aledo | 4 | Illinois | 3,552 | 3,618 | -0.48% | 1,515 | 2.34 |
| Orion | 5 | Illinois | 1,717 | 1,755 | -0.58% | 1,836 | 0.94 |
| Andalusia | 6 | Illinois | 1,151 | 1,181 | -0.69% | 980 | 1.18 |
| Viola | 7 | Illinois | 853 | 868 | -0.47% | 1,018 | 0.84 |
| Coyne Center | 8 | Illinois | 806 | 1,102 | -8.1% | 469 | 1.72 |
| Alexis | 9 | Illinois | 759 | 790 | -1.04% | 1,598 | 0.47 |
| Matherville | 10 | Illinois | 692 | 706 | -0.57% | 1,770 | 0.39 |
| Sherrard | 11 | Illinois | 689 | 693 | -0.14% | 742 | 0.93 |
| Windsor | 12 | Illinois | 658 | 665 | -0.3% | 1,502 | 0.44 |
| New Boston | 13 | Illinois | 610 | 612 | -0.16% | 648 | 0.94 |
| Keithsburg | 14 | Illinois | 546 | 545 | 0% | 213 | 2.56 |
| Andover | 15 | Illinois | 536 | 554 | -0.92% | 541 | 0.99 |
| Reynolds | 16 | Illinois | 479 | 499 | -1.03% | 1,302 | 0.37 |
| Oak Grove | 17 | Illinois | 462 | 469 | -0.43% | 702 | 0.66 |
| Joy | 18 | Illinois | 362 | 370 | -0.55% | 846 | 0.43 |
| Seaton | 19 | Illinois | 207 | 213 | -0.96% | 131 | 1.58 |
| Rio | 20 | Illinois | 202 | 209 | -0.98% | 647 | 0.31 |
| Ophiem | 21 | Illinois | 184 | 180 | -1.6% | 156 | 1.18 |
| North Henderson | 22 | Illinois | 160 | 162 | -0.62% | 708 | 0.23 |
| Preemption | 23 | Illinois | 142 | 172 | -3.4% | 128 | 1.11 |
| Cable | 24 | Illinois | 107 | 103 | 0.94% | 94 | 1.14 |
| Millersburg | 25 | Illinois | 48 | 76 | -12.73% | 162 | 0.30 |
| Illinois City | 26 | Illinois | 16 | 58 | -38.46% | 35 | 0.46 |
| Lynn Center | 27 | Illinois | 9 | 39 | -43.75% | 46 | 0.20 |
| Swedona | 28 | Illinois | 4 | 95 | -77.78% | 14 | 0.28 |
| Buffalo Prairie | 29 | Illinois | 0 | 27 | 0% | 0 | 3.76 |
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 Mercer County.
Buffalo Prairie is the smallest city in Mercer County.
There are 29 cities in Mercer County, Illinois.