Resident Population in Fairfax County, VA was 1141.87800 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Fairfax County, VA reached a record high of 1152.35900 in January of 2019 and a record low of 454.27500 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Fairfax County, VA - last updated from the United States Federal Reserve on May of 2024.