31 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Aux Sable | 1 | 15,996 | 15,368 | 0.64% | 550 | 29 | Township |
| Morris | 2 | 14,675 | 14,233 | 0.6% | 1,157 | 13 | City |
| Minooka | 3 | 12,945 | 12,755 | 0.29% | 1,422 | 9 | Village |
| Morris | 4 | 7,336 | 7,149 | 0.36% | 2,107 | 3 | Township |
| Braceville | 5 | 6,609 | 6,450 | 0.43% | 370 | 18 | Township |
| Saratoga | 6 | 6,590 | 6,401 | 0.43% | 183 | 36 | Township |
| Coal City | 7 | 5,837 | 5,701 | 0.46% | 1,012 | 6 | Village |
| Gardner | 8 | 4,583 | 4,641 | 0% | 108 | 43 | Township |
| Felix | 9 | 4,536 | 4,416 | 0.47% | 416 | 11 | Township |
| Diamond | 10 | 2,719 | 2,632 | 0.63% | 1,431 | 2 | Village |
| Erienna | 11 | 2,505 | 2,429 | 0.52% | 120 | 21 | Township |
| Wauponsee | 12 | 2,360 | 2,306 | 0.43% | 88 | 27 | Township |
| Goose Lake | 13 | 1,795 | 1,750 | 0.45% | 72 | 25 | Township |
| Mazon | 14 | 1,483 | 1,471 | 0.14% | 42 | 35 | Township |
| Garfield | 15 | 1,456 | 1,445 | 0.21% | 80 | 18 | Township |
| Gardner | 16 | 1,367 | 1,359 | 0.07% | 469 | 3 | Village |
| Mazon | 17 | 983 | 978 | 0.1% | 1,633 | 1 | Village |
| Braceville | 18 | 722 | 721 | 0% | 232 | 3 | Village |
| South Wilmington | 19 | 717 | 704 | 0.28% | 1,457 | 0 | Village |
| Godley | 20 | 649 | 573 | 2.37% | 599 | 1 | Village |
| Nettle Creek | 21 | 479 | 469 | 0.21% | 13 | 36 | Township |
| Carbon Hill | 22 | 385 | 375 | 0.52% | 2,115 | 0 | Village |
| Goodfarm | 23 | 351 | 340 | 0.86% | 10 | 36 | Township |
| Norman | 24 | 332 | 323 | 0.3% | 20 | 17 | Township |
| Maine | 25 | 315 | 310 | 0% | 18 | 18 | Township |
| Lisbon | 26 | 275 | 270 | 0.36% | 130 | 2 | Village |
| Plattville | 27 | 221 | 218 | 0% | 98 | 2 | Village |
| Verona | 28 | 207 | 205 | 0% | 1,255 | 0 | Village |
| Symerton | 29 | 123 | 125 | -0.81% | 783 | 0 | Village |
| Kinsman | 30 | 86 | 89 | -1.15% | 1,265 | 0 | Village |
| East Brooklyn | 31 | 79 | 77 | 0% | 1,519 | 0 | Village |
Aux Sable is the largest city in Grundy County, with a population of 15,996.
East Brooklyn is the smallest city in Grundy County, with a population of 79.
There are 31 cities in Grundy County, Illinois.