Resident Population in De Witt County, IL was 15.36500 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in De Witt County, IL reached a record high of 18.16800 in January of 1981 and a record low of 15.31000 in January of 2022. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in De Witt County, IL - last updated from the United States Federal Reserve on May of 2024.