Resident Population in Day County, SD was 5.45100 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Day County, SD reached a record high of 8.90000 in January of 1971 and a record low of 5.41400 in January of 2019. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Day County, SD - last updated from the United States Federal Reserve on May of 2024.