10 cities
| City | Rank | 2026 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Missouri Valley | 1 | 2,619 | 2,675 | -0.34% | 788 | 3 | City |
| Woodbine | 2 | 1,746 | 1,628 | 1.16% | 1,054 | 2 | City |
| Logan | 3 | 1,334 | 1,385 | -0.6% | 1,346 | 1 | City |
| Dunlap | 4 | 1,023 | 1,043 | -0.29% | 820 | 1 | City |
| Mondamin | 5 | 334 | 337 | 0% | 739 | 0 | City |
| Persia | 6 | 290 | 296 | -0.34% | 579 | 1 | City |
| Modale | 7 | 289 | 274 | 1.05% | 278 | 1 | City |
| Pisgah | 8 | 249 | 246 | 0.4% | 498 | 1 | City |
| Magnolia | 9 | 194 | 193 | 0% | 318 | 1 | City |
| Little Sioux | 10 | 172 | 166 | 0.58% | 459 | 0 | City |
Missouri Valley is the largest city in Harrison County, with a population of 2,619.
Little Sioux is the smallest city in Harrison County, with a population of 172.
There are 10 cities in Harrison County, Iowa.