Resident Population in Loudoun County, VA was 436.34700 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Loudoun County, VA reached a record high of 436.34700 in January of 2023 and a record low of 37.15000 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Loudoun County, VA - last updated from the United States Federal Reserve on May of 2024.