Resident Population in Richland County, IL was 15.48800 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Richland County, IL reached a record high of 18.51500 in January of 1982 and a record low of 15.41600 in January of 2008. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Richland County, IL - last updated from the United States Federal Reserve on May of 2024.