48 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Watseka | 1 | 4,408 | 4,669 | -0.97% | 1,497 | 3 | City |
| Middleport | 2 | 3,600 | 3,726 | 0.08% | 99 | 36 | Township |
| Chebanse | 3 | 2,792 | 2,871 | 0.18% | 44 | 64 | Township |
| Belmont | 4 | 2,356 | 2,431 | 0.13% | 65 | 36 | Township |
| Douglas | 5 | 1,972 | 2,043 | 0.1% | 44 | 45 | Township |
| Gilman | 6 | 1,640 | 1,741 | -1.03% | 500 | 3 | City |
| Onarga | 7 | 1,577 | 1,624 | 0.19% | 32 | 49 | Township |
| Milford | 8 | 1,427 | 1,484 | 0% | 32 | 44 | Township |
| Loda | 9 | 1,398 | 1,429 | 0.29% | 36 | 39 | Township |
| Ashkum | 10 | 1,379 | 1,421 | 0.15% | 22 | 62 | Township |
| Onarga | 11 | 1,271 | 1,340 | -0.86% | 759 | 2 | Village |
| Clifton | 12 | 1,269 | 1,347 | -1.01% | 1,365 | 1 | Village |
| Sheldon | 13 | 1,187 | 1,223 | 0.25% | 30 | 40 | Township |
| Milford | 14 | 1,087 | 1,159 | -1.09% | 1,620 | 1 | Village |
| Pigeon Grove | 15 | 1,078 | 1,121 | -0.09% | 30 | 36 | Township |
| Chebanse | 16 | 992 | 1,049 | -0.9% | 1,257 | 1 | Village |
| Sheldon | 17 | 911 | 968 | -0.98% | 1,210 | 1 | Village |
| Danforth | 18 | 859 | 887 | 0.12% | 17 | 52 | Township |
| Martinton | 19 | 804 | 831 | 0% | 15 | 54 | Township |
| Artesia | 20 | 799 | 827 | 0.13% | 14 | 57 | Township |
| Cissna Park | 21 | 761 | 811 | -1.04% | 1,050 | 1 | Village |
| Ashkum | 22 | 702 | 743 | -0.99% | 841 | 1 | Village |
| Ash Grove | 23 | 635 | 651 | 0.16% | 10 | 61 | Township |
| Danforth | 24 | 559 | 592 | -0.89% | 1,169 | 0 | Village |
| Iroquois | 25 | 536 | 550 | 0.37% | 15 | 36 | Township |
| Crescent City | 26 | 517 | 550 | -0.96% | 1,134 | 0 | Village |
| Crescent | 27 | 516 | 532 | 0.19% | 14 | 36 | Township |
| Beaverville | 28 | 492 | 508 | 0% | 13 | 38 | Township |
| Beaver | 29 | 462 | 473 | 0.43% | 14 | 34 | Township |
| Buckley | 30 | 458 | 488 | -1.08% | 1,449 | 0 | Village |
| Sun River Terrace | 31 | 445 | 459 | -0.45% | 766 | 1 | Village |
| Papineau | 32 | 426 | 437 | 0.24% | 14 | 29 | Township |
| Woodland | 33 | 336 | 348 | -0.59% | 9 | 38 | Township |
| Loda | 34 | 324 | 345 | -0.92% | 221 | 1 | Village |
| Martinton | 35 | 314 | 335 | -0.95% | 1,146 | 0 | Village |
| Ridgeland | 36 | 309 | 320 | 0% | 11 | 27 | Township |
| Fountain Creek | 37 | 294 | 302 | 0.34% | 8 | 36 | Township |
| Beaverville | 38 | 285 | 305 | -1.04% | 1,036 | 0 | Village |
| Woodland | 39 | 268 | 273 | -0.37% | 7 | 37 | Township |
| Donovan | 40 | 233 | 248 | -0.85% | 710 | 0 | Village |
| Woodland | 41 | 232 | 247 | -0.85% | 473 | 0 | Village |
| Thawville | 42 | 200 | 214 | -0.99% | 651 | 0 | Village |
| Stockland | 43 | 195 | 200 | 0% | 4 | 54 | Township |
| Wellington | 44 | 190 | 204 | -1.04% | 798 | 0 | Village |
| Prairie Green | 45 | 158 | 165 | -0.63% | 4 | 41 | Township |
| Milks Grove | 46 | 157 | 162 | 0% | 4 | 36 | Township |
| Iroquois | 47 | 129 | 134 | -0.77% | 228 | 1 | Village |
| Papineau | 48 | 127 | 135 | -0.78% | 611 | 0 | Village |
Watseka is the largest city in Iroquois County, with a population of 4,408.
Papineau is the smallest city in Iroquois County, with a population of 127.
There are 48 cities in Iroquois County, Illinois.