Resident Population in Merrimack County, NH was 157.10300 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Merrimack County, NH reached a record high of 157.10300 in January of 2023 and a record low of 80.92500 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Merrimack County, NH - last updated from the United States Federal Reserve on May of 2024.