Resident Population in Marion County, IA was 33.77000 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Marion County, IA reached a record high of 33.77000 in January of 2023 and a record low of 26.35200 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Marion County, IA - last updated from the United States Federal Reserve on May of 2024.