Resident Population in Harford County, MD was 264.64400 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Harford County, MD reached a record high of 264.64400 in January of 2023 and a record low of 115.37800 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Harford County, MD - last updated from the United States Federal Reserve on May of 2024.