26 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Trenton | 1 | 5,953 | 6,004 | -0.45% | 125 | 48 | Township |
| Trenton | 2 | 5,953 | 5,973 | -0.45% | 125 | 48 | Township |
| Trenton | 3 | 5,589 | 5,611 | 0.02% | 867 | 6 | City |
| Trenton | 4 | 5,589 | 5,582 | 0.02% | 867 | 6 | City |
| Jefferson | 5 | 471 | 474 | -0.42% | 13 | 36 | Township |
| Jefferson | 6 | 471 | 472 | -0.42% | 13 | 36 | Township |
| Wilson | 7 | 345 | 349 | -0.29% | 10 | 34 | Township |
| Wilson | 8 | 345 | 347 | -0.29% | 10 | 34 | Township |
| Marion | 9 | 258 | 260 | -0.39% | 6 | 42 | Township |
| Marion | 10 | 258 | 259 | -0.39% | 6 | 42 | Township |
| Spickard | 11 | 219 | 222 | -0.45% | 347 | 1 | City |
| Spickard | 12 | 219 | 221 | -0.45% | 347 | 1 | City |
| Leisure Lake | 13 | 209 | 130 | 1.46% | 150 | 1 | CDP |
| Galt | 14 | 166 | 167 | 0% | 580 | 0 | City |
| Galt | 15 | 166 | 166 | 0% | 580 | 0 | City |
| Myers | 16 | 159 | 159 | 0% | 5 | 35 | Township |
| Myers | 17 | 159 | 158 | 0% | 5 | 35 | Township |
| Laredo | 18 | 154 | 157 | -0.65% | 560 | 0 | City |
| Laredo | 19 | 154 | 156 | -0.65% | 560 | 0 | City |
| Edinburg | 20 | 109 | 84 | 6.86% | 102 | 1 | CDP |
| Harrison | 21 | 102 | 102 | 0% | 5 | 22 | Township |
| Harrison | 22 | 102 | 101 | 0% | 5 | 22 | Township |
| Tindall | 23 | 49 | 49 | 0% | 371 | 0 | Town |
| Tindall | 24 | 49 | 49 | 0% | 371 | 0 | Town |
| Osgood | 25 | 21 | 23 | -4.55% | 115 | 0 | Village |
| Osgood | 26 | 21 | 23 | -4.55% | 115 | 0 | Village |
Trenton is the largest city in Grundy County, with a population of 5,953.
Osgood is the smallest city in Grundy County, with a population of 21.
There are 26 cities in Grundy County, Missouri.