Resident Population in Massac County, IL was 13.66100 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Massac County, IL reached a record high of 15.38000 in January of 2010 and a record low of 13.60000 in January of 1971. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Massac County, IL - last updated from the United States Federal Reserve on May of 2024.