Founded in 1873, Hamlin County is one of 66 counties in the state of South Dakota. Historically, Hamlin County was formed from Deuel County. The city of Hayti is the county seat. With FIPS code of 57, Hamlin County has a population of 6,255 and area of 511 square miles (1,323 km2).
List of all cities in Hamlin County, SD alphabetically
| City/Town | Postal Code | Area Code |
| Alsville, SD | 57248 | 605 |
| Bryant, SD | 57221 | 605 |
| Castlewood, SD | 57223 | 605 |
| Dempster, SD | 57234 | 605 |
| Estelline, SD | 57234 | 605 |
| Hayti, SD | 57241 | 605 |
| Hazel, SD | 57242 | 605 |
| Kones Corner, SD | 57223 | 605 |
| Lake Norden, SD | 57248 | 605 |
| Thomas, SD | 57241 | 605 |