19 cities
| City | Rank | 2025 Pop. ↓ | 2020 Pop. | Annual Change | Density | Area (mi²) | Type |
|---|---|---|---|---|---|---|---|
| Armour | 1 | 715 | 697 | 0.42% | 757 | 1 | City |
| Corsica | 2 | 554 | 561 | -0.36% | 662 | 1 | City |
| Holland | 3 | 169 | 167 | 0% | 6 | 29 | Township |
| Delmont | 4 | 153 | 155 | -0.65% | 201 | 1 | City |
| Joubert | 5 | 144 | 142 | 0% | 5 | 29 | Township |
| Independence | 6 | 140 | 141 | 0% | 4 | 36 | Township |
| Valley | 7 | 134 | 132 | 0% | 4 | 36 | Township |
| Washington | 8 | 127 | 125 | 0% | 4 | 29 | Township |
| Walnut Grove | 9 | 114 | 115 | 0% | 4 | 29 | Township |
| Iowa | 10 | 88 | 88 | 0% | 2 | 36 | Township |
| Lincoln | 11 | 79 | 79 | 0% | 2 | 35 | Township |
| Grandview | 12 | 77 | 77 | 0% | 2 | 35 | Township |
| Garfield | 13 | 73 | 73 | 0% | 2 | 29 | Township |
| Belmont | 14 | 65 | 65 | 0% | 2 | 34 | Township |
| East Choteau | 15 | 36 | 36 | 0% | 2 | 16 | Township |
| Milltown | 16 | 31 | 25 | 6.9% | 70 | 0 | CDP |
| Harrison | 17 | 24 | 27 | -4% | 1 | 36 | Township |
| Harrison | 18 | 9 | 7 | 12.5% | 83 | 0 | CDP |
| New Holland | 19 | 5 | 8 | 0% | 43 | 0 | CDP |
Armour is the largest city in Douglas County, with a population of 715.
New Holland is the smallest city in Douglas County, with a population of 5.
There are 19 cities in Douglas County, South Dakota.