Resident Population in Johnson County, IA was 157.52800 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Johnson County, IA reached a record high of 157.52800 in January of 2023 and a record low of 72.12700 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Johnson County, IA - last updated from the United States Federal Reserve on May of 2024.