Resident Population in McLean County, IL was 172.06900 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, Resident Population in McLean County, IL reached a record high of 175.08700 in January of 2013 and a record low of 104.38900 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in McLean County, IL - last updated from the United States Federal Reserve on April of 2026.