Resident Population in St. Charles County, MO was 416.65900 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in St. Charles County, MO reached a record high of 416.65900 in January of 2023 and a record low of 92.95400 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in St. Charles County, MO - last updated from the United States Federal Reserve on May of 2024.