Resident Population in Mercer County, PA was 108.14000 Thous. of Persons in January of 2024, according to the United States Federal Reserve. Historically, Resident Population in Mercer County, PA reached a record high of 130.40000 in January of 1972 and a record low of 108.14000 in January of 2024. Trading Economics provides the current actual value, an historical data chart and related indicators for Resident Population in Mercer County, PA - last updated from the United States Federal Reserve on April of 2026.