Resident Population in Jefferson County, PA was 43.61200 Thous. of Persons in January of 2023, according to the United States Federal Reserve. Historically, Resident Population in Jefferson County, PA reached a record high of 48.60000 in January of 1979 and a record low of 43.29900 in January of 2019. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Jefferson County, PA - last updated from the United States Federal Reserve on May of 2024.