7 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Armour | 1 | 707 | 696 | 0.28% | 749 | 0.94 | City |
| Corsica | 2 | 552 | 561 | -0.36% | 659 | 0.84 | City |
| Delmont | 3 | 152 | 154 | 0% | 199 | 0.76 | City |
| Old Elm Spring Colony | 4 | 49 | 0 | 6.52% | 50 | 0.97 | CDP |
| Milltown | 5 | 31 | 25 | 6.9% | 70 | 0.44 | CDP |
| Harrison | 6 | 9 | 7 | 12.5% | 83 | 0.11 | CDP |
| New Holland | 7 | 5 | 8 | 0% | 43 | 0.12 | CDP |
Armour is the largest city in Douglas County, with a population of 707.
New Holland is the smallest city in Douglas County.
There are 7 cities in Douglas County, South Dakota.