Resident Population in Clay County, SD was 15.43100 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Clay County, SD reached a record high of 15.43100 in January of 2023 and a record low of 12.40000 in January of 1971. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Clay County, SD - last updated from the United States Federal Reserve on May of 2024.