Resident Population in Illinois was 12549.68900 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Illinois reached a record high of 12895.77800 in January of 2013 and a record low of 4828.00000 in January of 1900. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Illinois - last updated from the United States Federal Reserve on March of 2024.