Resident Population in Johnson County, IL was 13.32600 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Johnson County, IL reached a record high of 13.68800 in January of 2007 and a record low of 7.50000 in January of 1971. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Johnson County, IL - last updated from the United States Federal Reserve on May of 2024.