31 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Aux Sable | 1 | 16,098 | 15,368 | 0.64% | 553 | 29 | Township |
| Morris | 2 | 14,764 | 14,233 | 0.61% | 1,164 | 13 | City |
| Minooka | 3 | 12,983 | 12,755 | 0.29% | 1,427 | 9 | Village |
| Morris | 4 | 7,362 | 7,149 | 0.35% | 2,115 | 3 | Township |
| Braceville | 5 | 6,637 | 6,450 | 0.42% | 371 | 18 | Township |
| Saratoga | 6 | 6,618 | 6,401 | 0.42% | 184 | 36 | Township |
| Coal City | 7 | 5,864 | 5,701 | 0.46% | 1,017 | 6 | Village |
| Gardner | 8 | 4,583 | 4,641 | 0% | 108 | 43 | Township |
| Felix | 9 | 4,557 | 4,416 | 0.46% | 418 | 11 | Township |
| Diamond | 10 | 2,737 | 2,632 | 0.66% | 1,441 | 2 | Village |
| Erienna | 11 | 2,518 | 2,429 | 0.52% | 121 | 21 | Township |
| Wauponsee | 12 | 2,370 | 2,306 | 0.42% | 88 | 27 | Township |
| Goose Lake | 13 | 1,803 | 1,750 | 0.45% | 72 | 25 | Township |
| Mazon | 14 | 1,485 | 1,471 | 0.13% | 42 | 35 | Township |
| Garfield | 15 | 1,459 | 1,445 | 0.21% | 81 | 18 | Township |
| Gardner | 16 | 1,369 | 1,359 | 0.15% | 470 | 3 | Village |
| Mazon | 17 | 984 | 978 | 0.1% | 1,635 | 1 | Village |
| Braceville | 18 | 722 | 721 | 0% | 232 | 3 | Village |
| South Wilmington | 19 | 720 | 704 | 0.42% | 1,463 | 0 | Village |
| Godley | 20 | 664 | 573 | 2.31% | 613 | 1 | Village |
| Nettle Creek | 21 | 480 | 469 | 0.21% | 13 | 36 | Township |
| Carbon Hill | 22 | 387 | 375 | 0.52% | 2,126 | 0 | Village |
| Goodfarm | 23 | 354 | 340 | 0.85% | 10 | 36 | Township |
| Norman | 24 | 333 | 323 | 0.3% | 20 | 17 | Township |
| Maine | 25 | 315 | 310 | 0% | 18 | 18 | Township |
| Lisbon | 26 | 276 | 270 | 0.36% | 130 | 2 | Village |
| Plattville | 27 | 222 | 218 | 0.45% | 98 | 2 | Village |
| Verona | 28 | 208 | 205 | 0.48% | 1,261 | 0 | Village |
| Symerton | 29 | 123 | 125 | 0% | 783 | 0 | Village |
| Kinsman | 30 | 86 | 89 | 0% | 1,265 | 0 | Village |
| East Brooklyn | 31 | 80 | 77 | 1.27% | 1,538 | 0 | Village |
Aux Sable is the largest city in Grundy County, with a population of 16,098.
East Brooklyn is the smallest city in Grundy County, with a population of 80.
There are 31 cities in Grundy County, Illinois.