23 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Quincy | 1 | 38,398 | 39,410 | -0.52% | 2,435 | 15.77 | City |
| Camp Point | 2 | 1,108 | 1,123 | -0.27% | 875 | 1.27 | Village |
| Payson | 3 | 985 | 1,022 | -0.71% | 842 | 1.17 | Village |
| Mendon | 4 | 839 | 869 | -0.71% | 979 | 0.86 | Village |
| Golden | 5 | 620 | 645 | -0.8% | 966 | 0.64 | Village |
| Clayton | 6 | 609 | 638 | -0.98% | 689 | 0.88 | Village |
| Ursa | 7 | 582 | 607 | -0.85% | 843 | 0.69 | Village |
| Liberty | 8 | 517 | 541 | -0.96% | 1,322 | 0.39 | Village |
| Loraine | 9 | 291 | 298 | -0.34% | 345 | 0.84 | Village |
| Plainville | 10 | 261 | 271 | -0.76% | 1,111 | 0.23 | Village |
| Paloma | 11 | 158 | 174 | 7.48% | 543 | 0.29 | CDP |
| Coatsburg | 12 | 142 | 147 | -0.7% | 1,076 | 0.13 | Village |
| Lima | 13 | 142 | 147 | -0.7% | 1,052 | 0.14 | Village |
| Burton | 14 | 139 | 41 | 6.92% | 421 | 0.33 | CDP |
| Bloomfield | 15 | 123 | 99 | 7.9% | 237 | 0.52 | CDP |
| Columbus | 16 | 110 | 114 | -0.9% | 502 | 0.22 | Village |
| Fowler | 17 | 102 | 86 | 6.25% | 756 | 0.14 | CDP |
| Beverly | 18 | 87 | 110 | 6.1% | 63 | 1.38 | CDP |
| El Dara | 19 | 60 | 64 | -1.64% | 59 | 1.01 | Village |
| Adams | 20 | 49 | 44 | 6.52% | 22 | 2.24 | CDP |
| Marcelline | 21 | 44 | 76 | 7.32% | 880 | 0.05 | CDP |
| La Prairie | 22 | 38 | 40 | 0% | 197 | 0.19 | Village |
| Meyer | 23 | 24 | 0 | 9.09% | 169 | 0.14 | CDP |
Quincy is the largest city in Adams County, with a population of 38,398.
Meyer is the smallest city in Adams County.
There are 23 cities in Adams County, Illinois.