It is the smallest unincorporated county seat in the United States.

Spencer donated 30 acres, resulting in the community becoming the county seat.

[8] The center of population of South Dakota is located in Gann Valley.

[9] Gann Valley holds the record for the highest temperature in South Dakota, at 120 °F (49 °C).

[10] This climatic region is typified by large seasonal temperature differences, with warm to hot (and often humid) summers and cold (sometimes severely cold) winters.