Resident Population in Clinton County, IL was 36.78500 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Clinton County, IL reached a record high of 38.02400 in January of 2011 and a record low of 28.31500 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Clinton County, IL - last updated from the United States Federal Reserve on May of 2024.