47 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Quincy | 1 | 38,729 | 39,410 | -0.1% | 2,456 | 16 | Township |
| Quincy | 2 | 38,398 | 39,410 | -0.52% | 2,435 | 16 | City |
| Melrose | 3 | 5,606 | 5,741 | -0.23% | 125 | 45 | Township |
| Ellington | 4 | 2,734 | 2,821 | -0.36% | 80 | 34 | Township |
| Payson | 5 | 1,701 | 1,751 | -0.29% | 44 | 38 | Township |
| Camp Point | 6 | 1,600 | 1,630 | -0.25% | 43 | 38 | Township |
| Mendon | 7 | 1,389 | 1,427 | -0.22% | 38 | 37 | Township |
| Liberty | 8 | 1,331 | 1,375 | -0.37% | 36 | 37 | Township |
| Gilmer | 9 | 1,122 | 1,161 | -0.44% | 30 | 37 | Township |
| Camp Point | 10 | 1,108 | 1,123 | -0.27% | 875 | 1 | Village |
| Ursa | 11 | 1,080 | 1,118 | -0.46% | 19 | 57 | Township |
| Payson | 12 | 985 | 1,022 | -0.71% | 842 | 1 | Village |
| Clayton | 13 | 902 | 935 | -0.44% | 24 | 37 | Township |
| Burton | 14 | 891 | 920 | -0.45% | 23 | 38 | Township |
| Mendon | 15 | 839 | 869 | -0.71% | 979 | 1 | Village |
| Northeast | 16 | 817 | 841 | -0.24% | 22 | 37 | Township |
| Liberty | 17 | 723 | 736 | -0.14% | 40 | 18 | Township |
| Honey Creek | 18 | 701 | 723 | -0.28% | 19 | 37 | Township |
| Clayton | 19 | 634 | 637 | 0.32% | 18 | 36 | Township |
| Golden | 20 | 620 | 645 | -0.8% | 966 | 1 | Village |
| Clayton | 21 | 609 | 638 | -0.98% | 689 | 1 | Village |
| Keene | 22 | 591 | 605 | -0.34% | 16 | 36 | Township |
| Ursa | 23 | 582 | 607 | -0.85% | 843 | 1 | Village |
| Columbus | 24 | 554 | 570 | -0.18% | 15 | 37 | Township |
| Liberty | 25 | 517 | 541 | -0.96% | 1,322 | 0 | Village |
| Fall Creek | 26 | 516 | 529 | -0.39% | 14 | 36 | Township |
| Lima | 27 | 499 | 514 | -0.4% | 9 | 55 | Township |
| Richfield | 28 | 394 | 407 | -0.25% | 10 | 38 | Township |
| La Prairie | 29 | 349 | 346 | 0.58% | 10 | 36 | Township |
| Beverly | 30 | 346 | 355 | -0.29% | 9 | 37 | Township |
| Loraine | 31 | 291 | 298 | -0.34% | 345 | 1 | Village |
| Plainville | 32 | 261 | 271 | -0.76% | 1,111 | 0 | Village |
| Loraine | 33 | 253 | 256 | 0% | 7 | 35 | Township |
| Houston | 34 | 208 | 215 | -0.48% | 5 | 38 | Township |
| McKee | 35 | 177 | 181 | 0% | 5 | 36 | Township |
| Paloma | 36 | 158 | 174 | 7.48% | 543 | 0 | CDP |
| Coatsburg | 37 | 142 | 147 | -0.7% | 1,076 | 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 | 110 | 114 | -0.9% | 502 | 0 | Village |
| Fowler | 42 | 102 | 86 | 6.25% | 756 | 0 | CDP |
| Beverly | 43 | 87 | 110 | 6.1% | 63 | 1 | CDP |
| El Dara | 44 | 60 | 64 | -1.64% | 59 | 1 | Village |
| Adams | 45 | 49 | 44 | 6.52% | 22 | 2 | CDP |
| Marcelline | 46 | 44 | 76 | 7.32% | 880 | 0 | CDP |
| La Prairie | 47 | 38 | 40 | 0% | 197 | 0 | Village |
Quincy is the largest city in Adams County, with a population of 38,729.
La Prairie is the smallest city in Adams County, with a population of 38.
There are 47 cities in Adams County, Illinois.