About Gann Valley, South Dakota
Gann Valley is an unincorporated community in and the county seat of Buffalo County, South Dakota, United States. The town had a population of 14 as of the 2010 census, and has been assigned the ZIP code of 57341. The center of population of South Dakota is located in Gann Valley. Gann Valley holds the record for the hottest temperature in South Dakota (120 degrees Fareinheit).