| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density (/mi²) | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Guttenberg | 1 | 1,786 | 1,817 | -0.17% | 814 | 2 | City |
| Monona | 2 | 1,442 | 1,474 | -0.14% | 1,059 | 1 | City |
| Elkader | 3 | 1,179 | 1,214 | -0.34% | 862 | 1 | City |
| Strawberry Point | 4 | 1,122 | 1,154 | -0.36% | 537 | 2 | City |
| Edgewood | 5 | 907 | 907 | 0.11% | 945 | 1 | City |
| Garnavillo | 6 | 737 | 754 | -0.27% | 781 | 1 | City |
| McGregor | 7 | 719 | 738 | -0.14% | 556 | 1 | City |
| Marquette | 8 | 438 | 427 | 0.46% | 236 | 2 | City |
| Luana | 9 | 310 | 300 | 0.32% | 281 | 1 | City |
| Farmersburg | 10 | 261 | 272 | -0.76% | 641 | 0 | City |
| Volga | 11 | 198 | 204 | -0.5% | 263 | 1 | City |
| North Buena Vista | 12 | 107 | 106 | 0% | 115 | 1 | City |
| St. Olaf | 13 | 97 | 103 | -1.02% | 402 | 0 | City |
| Balltown | 14 | 76 | 76 | 0% | 1,056 | 0 | City |
| Garber | 15 | 76 | 77 | -1.3% | 338 | 0 | City |
| Clayton | 16 | 44 | 46 | -2.22% | 86 | 1 | City |
| Osterdock | 17 | 42 | 44 | -2.33% | 106 | 0 | City |
| Elkport | 18 | 27 | 28 | 0% | 108 | 0 | City |
Guttenberg is the largest city in Clayton County, with a population of 1,786.
Elkport is the smallest city in Clayton County, with a population of 27.
There are 18 cities in Clayton County, Iowa.