Resident Population in Marshall County, IL was 11.68300 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Marshall County, IL reached a record high of 14.52400 in January of 1981 and a record low of 11.46300 in January of 2019. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Marshall County, IL - last updated from the United States Federal Reserve on May of 2024.