47 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Quincy | 1 | 38,613 | 39,575 | -0.45% | 2,449 | 16 | Township |
| Quincy | 2 | 38,588 | 39,575 | -0.51% | 2,447 | 16 | City |
| Melrose | 3 | 5,468 | 5,639 | -0.58% | 122 | 45 | Township |
| Ellington | 4 | 2,702 | 2,805 | -0.66% | 79 | 34 | Township |
| Payson | 5 | 1,695 | 1,754 | -0.47% | 44 | 38 | Township |
| Camp Point | 6 | 1,600 | 1,627 | -0.12% | 43 | 38 | Township |
| Mendon | 7 | 1,374 | 1,428 | -0.79% | 37 | 37 | Township |
| Liberty | 8 | 1,323 | 1,374 | -0.75% | 36 | 37 | Township |
| Gilmer | 9 | 1,117 | 1,160 | -0.62% | 30 | 37 | Township |
| Camp Point | 10 | 1,114 | 1,126 | -0.27% | 880 | 1 | Village |
| Ursa | 11 | 1,079 | 1,121 | -0.64% | 19 | 57 | Township |
| Payson | 12 | 991 | 1,025 | -0.7% | 847 | 1 | Village |
| Clayton | 13 | 900 | 939 | -0.88% | 24 | 37 | Township |
| Burton | 14 | 885 | 918 | -0.67% | 23 | 38 | Township |
| Mendon | 15 | 837 | 869 | -0.83% | 977 | 1 | Village |
| Northeast | 16 | 815 | 843 | -0.49% | 22 | 37 | Township |
| Liberty | 17 | 727 | 735 | 0% | 40 | 18 | Township |
| Honey Creek | 18 | 701 | 730 | -0.71% | 19 | 37 | Township |
| Clayton | 19 | 630 | 638 | -0.16% | 18 | 36 | Township |
| Golden | 20 | 621 | 648 | -0.96% | 967 | 1 | Village |
| Clayton | 21 | 610 | 639 | -0.97% | 690 | 1 | Village |
| Keene | 22 | 586 | 606 | -0.68% | 16 | 36 | Township |
| Ursa | 23 | 583 | 607 | -0.85% | 845 | 1 | Village |
| Columbus | 24 | 545 | 567 | -0.73% | 15 | 37 | Township |
| Liberty | 25 | 518 | 540 | -0.96% | 1,325 | 0 | Village |
| Fall Creek | 26 | 512 | 529 | -0.58% | 14 | 36 | Township |
| Lima | 27 | 494 | 513 | -0.6% | 9 | 55 | Township |
| Richfield | 28 | 394 | 409 | -0.51% | 10 | 38 | Township |
| Beverly | 29 | 342 | 355 | -0.58% | 9 | 37 | Township |
| La Prairie | 30 | 338 | 345 | -0.88% | 9 | 36 | Township |
| Loraine | 31 | 292 | 300 | -0.68% | 346 | 1 | Village |
| Plainville | 32 | 257 | 270 | -1.15% | 1,094 | 0 | Village |
| Loraine | 33 | 250 | 256 | -0.4% | 7 | 35 | Township |
| Houston | 34 | 207 | 214 | -0.48% | 5 | 38 | Township |
| McKee | 35 | 174 | 184 | -1.69% | 5 | 36 | Township |
| Paloma | 36 | 158 | 174 | 7.48% | 543 | 0 | CDP |
| Coatsburg | 37 | 148 | 153 | -0.67% | 1,121 | 0 | Village |
| Lima | 38 | 142 | 147 | -0.7% | 1,052 | 0 | Village |
| Burton | 39 | 139 | 41 | 6.92% | 421 | 0 | CDP |
| Bloomfield | 40 | 123 | 99 | 7.89% | 237 | 1 | CDP |
| Columbus | 41 | 108 | 113 | -0.92% | 493 | 0 | Village |
| Fowler | 42 | 102 | 86 | 6.25% | 756 | 0 | CDP |
| Beverly | 43 | 87 | 110 | 6.1% | 63 | 1 | CDP |
| El Dara | 44 | 61 | 63 | -1.61% | 60 | 1 | Village |
| Adams | 45 | 49 | 44 | 6.52% | 22 | 2 | CDP |
| Marcelline | 46 | 44 | 76 | 7.32% | 880 | 0 | CDP |
| La Prairie | 47 | 39 | 41 | -2.5% | 202 | 0 | Village |
Quincy is the largest city in Adams County, with a population of 38,613.
La Prairie is the smallest city in Adams County, with a population of 39.
There are 47 cities in Adams County, Illinois.