48 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Watseka | 1 | 4,451 | 4,669 | -0.98% | 1,512 | 3 | City |
| Middleport | 2 | 3,597 | 3,726 | 0.08% | 99 | 36 | Township |
| Chebanse | 3 | 2,787 | 2,871 | 0.18% | 44 | 64 | Township |
| Belmont | 4 | 2,353 | 2,431 | 0.13% | 65 | 36 | Township |
| Douglas | 5 | 1,970 | 2,043 | 0.1% | 44 | 45 | Township |
| Gilman | 6 | 1,657 | 1,741 | -1.02% | 681 | 2 | City |
| Onarga | 7 | 1,574 | 1,624 | 0.19% | 32 | 49 | Township |
| Milford | 8 | 1,427 | 1,484 | 0% | 32 | 44 | Township |
| Loda | 9 | 1,394 | 1,429 | 0.29% | 36 | 39 | Township |
| Ashkum | 10 | 1,377 | 1,421 | 0.15% | 22 | 62 | Township |
| Clifton | 11 | 1,282 | 1,347 | -1% | 1,378 | 1 | Village |
| Onarga | 12 | 1,282 | 1,340 | -0.93% | 766 | 2 | Village |
| Sheldon | 13 | 1,184 | 1,223 | 0.25% | 30 | 40 | Township |
| Milford | 14 | 1,099 | 1,159 | -1.08% | 1,638 | 1 | Village |
| Pigeon Grove | 15 | 1,079 | 1,121 | -0.09% | 30 | 36 | Township |
| Chebanse | 16 | 1,001 | 1,049 | -0.99% | 841 | 1 | Village |
| Sheldon | 17 | 920 | 968 | -1.08% | 1,222 | 1 | Village |
| Danforth | 18 | 858 | 887 | 0.12% | 17 | 52 | Township |
| Martinton | 19 | 804 | 831 | 0% | 15 | 54 | Township |
| Artesia | 20 | 798 | 827 | 0.13% | 14 | 57 | Township |
| Cissna Park | 21 | 769 | 811 | -1.16% | 1,061 | 1 | Village |
| Ashkum | 22 | 709 | 743 | -0.98% | 849 | 1 | Village |
| Ash Grove | 23 | 634 | 651 | 0.16% | 10 | 61 | Township |
| Danforth | 24 | 564 | 592 | -1.05% | 1,180 | 0 | Village |
| Iroquois | 25 | 534 | 550 | 0.38% | 15 | 36 | Township |
| Crescent City | 26 | 522 | 550 | -1.14% | 1,145 | 0 | Village |
| Crescent | 27 | 515 | 532 | 0.19% | 14 | 36 | Township |
| Beaverville | 28 | 492 | 508 | 0% | 13 | 38 | Township |
| Buckley | 29 | 463 | 488 | -1.07% | 1,465 | 0 | Village |
| Beaver | 30 | 460 | 473 | 0.44% | 14 | 34 | Township |
| Sun River Terrace | 31 | 447 | 459 | -0.67% | 769 | 1 | Village |
| Papineau | 32 | 425 | 437 | 0.24% | 14 | 29 | Township |
| Woodland | 33 | 338 | 348 | -0.59% | 9 | 38 | Township |
| Loda | 34 | 327 | 345 | -1.21% | 223 | 1 | Village |
| Martinton | 35 | 317 | 335 | -1.25% | 1,157 | 0 | Village |
| Ridgeland | 36 | 309 | 320 | 0% | 11 | 27 | Township |
| Fountain Creek | 37 | 293 | 302 | 0.34% | 8 | 36 | Township |
| Beaverville | 38 | 288 | 305 | -1.37% | 1,047 | 0 | Village |
| Woodland | 39 | 269 | 273 | -0.37% | 7 | 37 | Township |
| Donovan | 40 | 235 | 248 | -1.26% | 716 | 0 | Village |
| Woodland | 41 | 234 | 247 | -1.27% | 478 | 0 | Village |
| Thawville | 42 | 202 | 214 | -1.46% | 658 | 0 | Village |
| Stockland | 43 | 195 | 200 | 0% | 4 | 54 | Township |
| Wellington | 44 | 192 | 204 | -1.54% | 807 | 0 | Village |
| Prairie Green | 45 | 159 | 165 | -0.63% | 4 | 41 | Township |
| Milks Grove | 46 | 157 | 162 | 0% | 4 | 36 | Township |
| Iroquois | 47 | 130 | 134 | -0.76% | 229 | 1 | Village |
| Papineau | 48 | 128 | 135 | -1.54% | 615 | 0 | Village |
Watseka is the largest city in Iroquois County, with a population of 4,451.
Papineau is the smallest city in Iroquois County, with a population of 128.
There are 48 cities in Iroquois County, Illinois.