Resident Population in Jefferson County, NY was 113.14000 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, Resident Population in Jefferson County, NY reached a record high of 120.33500 in January of 2012 and a record low of 87.30200 in January of 1982. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Jefferson County, NY - last updated from the United States Federal Reserve on April of 2026.