
Northumberland County
- State:
- Pennsylvania
- County Seat:
- Sunbury
Northumberland County's estimated 2025 population is 90,114 with a growth rate of 0% in the past year according to the most recent United States census data. Northumberland County is the 32nd largest county in Pennsylvania. The 2010 population was 94,287 and has seen a growth of -4.43% since that time.