Founded in 1873, Dewey County is one of 66 counties in the state of South Dakota. Historically, Dewey County was formed from Armstrong County and Indian lands. The city of Timber Lake is the county seat. With FIPS code of 41, Dewey County has a population of 5,246 and area of 2,303 square miles (5,965 km2).
List of all cities in Dewey County, SD alphabetically
| City/Town | Postal Code | Area Code |
| Cheyenne River Reservation, SD | 57625 | 605 |
| Eagle Butte, SD | 57625 | 605 |
| Firesteel, SD | 57633 | 605 |
| Glencross, SD | 57630 | 605 |
| Isabel, SD | 57633 | 605 |
| La Plant, SD | 57652 | 605 |
| Lantry, SD | 57636 | 605 |
| Lightcap, SD | 57633 | 605 |
| Parade, SD | 57625 | 605 |
| Ridgeview, SD | 57652 | 605 |
| Standing Rock Reservation, SD | 57625 | 605 |
| Timber Lake, SD | 57656 | 605 |
| Whitehorse, SD | 57661 | 605 |