13 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Missouri Valley | 1 | 2,642 | 2,677 | -0.26% | 795 | 3.32 | City |
| Woodbine | 2 | 1,778 | 1,627 | 1.72% | 1,074 | 1.66 | City |
| Logan | 3 | 1,332 | 1,386 | -0.82% | 1,344 | 0.99 | City |
| Dunlap | 4 | 1,031 | 1,041 | -0.19% | 826 | 1.25 | City |
| Mondamin | 5 | 337 | 337 | 0% | 746 | 0.45 | City |
| Persia | 6 | 291 | 296 | -0.34% | 581 | 0.50 | City |
| Modale | 7 | 284 | 274 | 0.71% | 273 | 1.04 | City |
| Pisgah | 8 | 247 | 242 | 0.41% | 494 | 0.50 | City |
| Bentley | 9 | 198 | 158 | 2.59% | 193 | 1.03 | CDP |
| Magnolia | 10 | 188 | 187 | 0% | 308 | 0.61 | City |
| Little Sioux | 11 | 172 | 167 | 0.58% | 459 | 0.38 | City |
| California Junction | 12 | 98 | 40 | 7.69% | 213 | 0.46 | CDP |
| River Sioux | 13 | 6 | 40 | 0% | 16 | 0.38 | CDP |
Missouri Valley is the largest city in Harrison County, with a population of 2,642.
River Sioux is the smallest city in Harrison County.
There are 13 cities in Harrison County, Iowa.