Founded in 1862, Yankton County is one of 66 counties in the state of South Dakota. Historically, Yankton County was formed from unorganized territory. The city of Yankton is the county seat. With FIPS code of 135, Yankton County has a population of 23,297 and area of 522 square miles (1,352 km2).
List of all cities in Yankton County, SD alphabetically
| City/Town | Postal Code | Area Code |
| Gayville, SD | 57031 | 605 |
| Janesville, SD | 57067 | 605 |
| Lesterville, SD | 57040 | 605 |
| Mission Hill, SD | 57046 | 605 |
| Utica, SD | 57067 | 605 |
| Volin, SD | 57072 | 605 |
| Yankton, SD | 57078 | 605 |