County Population 2020 Population change 2010-2020 Pecentage change 2010-2020
Philadelphia County1,603,79777,7915.1%
Montgomery County856,55356,6797.1%
Chester County534,41335,5277.1%
Lancaster County552,98433,5396.5%
Allegheny County1,250,57827,2302.2%
Lehigh County374,55725,0607.2%
Cumberland County259,46924,06310.2%
York County456,43821,4664.9%
Bucks County646,53821,2893.4%
Dauphin County286,40118,3016.8%