36 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Aux Sable | 1 | 16,105 | 15,373 | 0.95% | 554 | 29 | Township |
| Morris | 2 | 14,705 | 14,212 | 0.68% | 1,187 | 12 | City |
| Minooka | 3 | 12,958 | 12,760 | 0.31% | 1,380 | 9 | Village |
| Morris | 4 | 7,371 | 7,130 | 0.72% | 2,117 | 3 | Township |
| Saratoga | 5 | 6,646 | 6,402 | 0.82% | 185 | 36 | Township |
| Braceville | 6 | 6,641 | 6,448 | 0.68% | 372 | 18 | Township |
| Coal City | 7 | 5,842 | 5,697 | 0.5% | 1,013 | 6 | Village |
| Felix | 8 | 4,568 | 4,413 | 0.82% | 419 | 11 | Township |
| Gardner | 9 | 4,533 | 4,646 | -0.42% | 107 | 43 | Township |
| Diamond | 10 | 2,718 | 2,627 | 0.67% | 1,431 | 2 | Village |
| Erienna | 11 | 2,511 | 2,421 | 0.8% | 121 | 21 | Township |
| Wauponsee | 12 | 2,373 | 2,305 | 0.72% | 89 | 27 | Township |
| Goose Lake | 13 | 1,807 | 1,750 | 0.78% | 73 | 25 | Township |
| Mazon | 14 | 1,496 | 1,470 | 0.54% | 43 | 35 | Township |
| Garfield | 15 | 1,466 | 1,445 | 0.55% | 81 | 18 | Township |
| Gardner | 16 | 1,366 | 1,358 | 0.15% | 469 | 3 | Village |
| Mazon | 17 | 981 | 978 | 0.1% | 1,630 | 1 | Village |
| Braceville | 18 | 724 | 721 | 0.14% | 233 | 3 | Village |
| South Wilmington | 19 | 723 | 705 | 0.56% | 1,470 | 0 | Village |
| Godley | 20 | 667 | 572 | 2.93% | 616 | 1 | Village |
| Rest Haven | 21 | 624 | 550 | 7.22% | 912 | 1 | CDP |
| Custer Park | 22 | 555 | 497 | 7.14% | 3,535 | 0 | CDP |
| Nettle Creek | 23 | 489 | 471 | 1.03% | 14 | 36 | Township |
| Carbon Hill | 24 | 386 | 375 | 0.52% | 2,121 | 0 | Village |
| Lakewood Shores | 25 | 351 | 566 | -15.83% | 1,009 | 0 | CDP |
| Goodfarm | 26 | 351 | 342 | 0.57% | 10 | 36 | Township |
| Norman | 27 | 340 | 325 | 1.19% | 20 | 17 | Township |
| Maine | 28 | 317 | 308 | 0.63% | 18 | 18 | Township |
| Lisbon | 29 | 277 | 271 | 0.36% | 131 | 2 | Village |
| Plattville | 30 | 224 | 219 | 0.45% | 99 | 2 | Village |
| Verona | 31 | 212 | 206 | 0.47% | 1,285 | 0 | Village |
| Ritchie | 32 | 193 | 164 | 7.22% | 187 | 1 | CDP |
| Symerton | 33 | 122 | 126 | -0.81% | 777 | 0 | Village |
| Kinsman | 34 | 90 | 90 | 0% | 1,324 | 0 | Village |
| East Brooklyn | 35 | 83 | 80 | 1.22% | 1,596 | 0 | Village |
| Lorenzo | 36 | 75 | 31 | 7.14% | 243 | 0 | CDP |
Aux Sable is the largest city in Grundy County, with a population of 16,105.
Lorenzo is the smallest city in Grundy County, with a population of 75.
There are 36 cities in Grundy County, Illinois.