Resident Population in Sullivan County, NH was 44.01200 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, Resident Population in Sullivan County, NH reached a record high of 44.01200 in January of 2024 and a record low of 30.94900 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Sullivan County, NH - last updated from the United States Federal Reserve on April of 2026.