Resident Population in Sullivan County, NY was 80.45000 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, Resident Population in Sullivan County, NY reached a record high of 80.45000 in January of 2024 and a record low of 52.58000 in January of 1970. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Sullivan County, NY - last updated from the United States Federal Reserve on April of 2026.