Resident Population in Union County, SD was 17.18300 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Union County, SD reached a record high of 17.18300 in January of 2023 and a record low of 9.64300 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Union County, SD - last updated from the United States Federal Reserve on May of 2024.