
Jefferson County
- State:
- Pennsylvania
- County Seat:
- Brookville
Jefferson County's estimated 2025 population is 43,374 with a growth rate of -0.27% in the past year according to the most recent United States census data. Jefferson County is the 49th largest county in Pennsylvania. The 2010 population was 45,163 and has seen a growth of -3.96% since that time.