19 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 |
| Holland township | 3 | 173 | 166 | 1.76% | 6 | 29.29 | Township |
| Delmont | 4 | 152 | 154 | 0% | 199 | 0.76 | City |
| Joubert township | 5 | 148 | 143 | 1.37% | 5 | 28.86 | Township |
| Independence township | 6 | 145 | 142 | 1.4% | 4 | 35.99 | Township |
| Valley township | 7 | 137 | 131 | 1.48% | 4 | 36.05 | Township |
| Washington township | 8 | 135 | 127 | 2.27% | 5 | 29.13 | Township |
| Walnut Grove township | 9 | 113 | 110 | 1.8% | 4 | 28.98 | Township |
| Iowa township | 10 | 91 | 90 | 1.11% | 3 | 35.52 | Township |
| Lincoln township | 11 | 83 | 79 | 2.47% | 2 | 35.48 | Township |
| Grandview township | 12 | 81 | 77 | 2.53% | 2 | 34.64 | Township |
| Garfield township | 13 | 80 | 76 | 2.56% | 3 | 29.30 | Township |
| Belmont township | 14 | 70 | 66 | 2.94% | 2 | 34.22 | Township |
| East Choteau township | 15 | 37 | 35 | 2.78% | 2 | 15.89 | Township |
| Milltown | 16 | 31 | 25 | 6.9% | 70 | 0.44 | CDP |
| Harrison township | 17 | 26 | 27 | 0% | 1 | 35.77 | Township |
| Harrison | 18 | 9 | 7 | 12.5% | 83 | 0.11 | CDP |
| New Holland | 19 | 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 19 cities in Douglas County, South Dakota.