Resident Population in McDonough County, IL was 26.83900 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in McDonough County, IL reached a record high of 40.60000 in January of 1973 and a record low of 26.83900 in January of 2023. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in McDonough County, IL - last updated from the United States Federal Reserve on May of 2024.