Resident Population in Jefferson County, KS was 18.32700 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Jefferson County, KS reached a record high of 19.16500 in January of 2019 and a record low of 11.94500 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Jefferson County, KS - last updated from the United States Federal Reserve on May of 2024.