
Allegheny County
- State:
- Pennsylvania
- County Seat:
- Pittsburgh
Allegheny County's estimated 2025 population is 1,209,265 with a growth rate of -0.64% in the past year according to the most recent United States census data. Allegheny County is the 2nd largest county in Pennsylvania. The 2010 population was 1,223,973 and has seen a growth of -1.2% since that time.