Resident Population in Middlesex County, MA was 1623.95200 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Middlesex County, MA reached a record high of 1628.67100 in January of 2020 and a record low of 1367.03400 in January of 1980. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Middlesex County, MA - last updated from the United States Federal Reserve on May of 2024.