The Pennsylvania State Data Center released a data brief showing estimated population changes at the county level from 2020 through July 1, 2025, based on recently released U.S. Census Bureau data. Population estimates are calculated using administrative records to estimate births, deaths, and migration.  

Pennsylvania experienced an overall population increase of just over 56,600 (+0.4%) between 2020 and 2025. Pike County and Cumberland County were the fastest-growing counties by percent change, while Chester and Montgomery counties saw the largest numeric increase.  

Philadelphia (-29,519) and Allegheny (-25,546) counties lost the most numeric population. Ten counties experienced population decreases of 3% or more from 2020 to 2025, including Cambria, Cameron, Clearfield, Elk, Fayette, Forest, Greene, McKean, Potter, and Warren.  

Across the state, deaths outpaced births, with only eight counties (led by Philadelphia) that had more births than deaths. During this same time, 54,300 residents left the state while 196,700 international migrants moved into Pennsylvania for a net positive migration of just under 142,500.  

For an interactive map of these population changes by county, click here. To reach the full Penn State Data Center research brief, click here.