10 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Missouri Valley | 1 | 2,628 | 2,675 | -0.38% | 791 | 3 | City |
| Woodbine | 2 | 1,726 | 1,628 | 1.11% | 1,042 | 2 | City |
| Logan | 3 | 1,342 | 1,385 | -0.67% | 1,354 | 1 | City |
| Dunlap | 4 | 1,026 | 1,043 | -0.39% | 822 | 1 | City |
| Mondamin | 5 | 334 | 337 | -0.3% | 739 | 0 | City |
| Persia | 6 | 291 | 296 | -0.34% | 581 | 1 | City |
| Modale | 7 | 286 | 274 | 0.7% | 275 | 1 | City |
| Pisgah | 8 | 248 | 246 | 0% | 496 | 1 | City |
| Magnolia | 9 | 194 | 193 | 0% | 318 | 1 | City |
| Little Sioux | 10 | 171 | 166 | 0.59% | 456 | 0 | City |
Missouri Valley is the largest city in Harrison County, with a population of 2,628.
Little Sioux is the smallest city in Harrison County, with a population of 171.
There are 10 cities in Harrison County, Iowa.