18 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| McLeansboro | 1 | 3,537 | 3,677 | -0.84% | 99 | 36 | Township |
| Dale | 2 | 1,238 | 1,232 | 0.16% | 36 | 35 | Township |
| Dahlgren | 3 | 1,094 | 1,147 | -1.08% | 20 | 54 | Township |
| Knight Prairie | 4 | 512 | 533 | -0.97% | 14 | 36 | Township |
| Dahlgren | 5 | 488 | 503 | -0.41% | 480 | 1 | Village |
| Twigg | 6 | 478 | 494 | -0.83% | 13 | 36 | Township |
| Mayberry | 7 | 425 | 444 | -0.93% | 8 | 55 | Township |
| Crouch | 8 | 367 | 381 | -0.81% | 8 | 47 | Township |
| Flannigan | 9 | 303 | 313 | -0.66% | 8 | 36 | Township |
| Broughton | 10 | 295 | 300 | 0% | 8 | 35 | Township |
| Crook | 11 | 280 | 288 | -0.71% | 8 | 36 | Township |
| Beaver Creek | 12 | 241 | 256 | -1.63% | 7 | 37 | Township |
| South Crouch | 13 | 191 | 199 | -0.52% | 8 | 25 | Township |
| Broughton | 14 | 177 | 183 | -0.56% | 94 | 2 | Village |
| South Flannigan | 15 | 136 | 141 | -0.73% | 7 | 18 | Township |
| South Twigg | 16 | 118 | 120 | 0% | 6 | 18 | Township |
| Belle Prairie City | 17 | 45 | 47 | 0% | 103 | 0 | Town |
| Macedonia | 18 | 29 | 29 | 0% | 107 | 0 | Village |
McLeansboro is the largest city in Hamilton County, with a population of 3,537.
Macedonia is the smallest city in Hamilton County, with a population of 29.
There are 18 cities in Hamilton County, Illinois.