Population of Counties in Pennsylvania (2021)

Two counties in the state of Pennsylvania have populations of more than one million. These are Philadelphia County, which is coterminous with the city of Philadelphia and has a population of 1,574,765 (even though it is the second smallest county in the state by land area), and Allegheny County, with its 1,227,553 residents. As of 2018, both of these counties have grown their populations since the last census, with Philadelphia County increasing by 3.04% and Allegheny County by a more modest 0.30%.

A number of other counties in Pennsylvania, while not quite as large, still have substantial populations. Montgomery County (820,656), Bucks County (626,751), and Delaware County (563,995) are all in the top five most populous counties in the state, and census statistics show that each of these have also had population increases of between 0.21% and 2.46% in recent years. Conversely, many counties in Pennsylvania have populations of fewer than fifty thousand residents. These include Forest County (7,306), Juniata County (24,475), and Susquehanna County (41,238).

In general, the population increases in Pennsylvania's counties are fairly modest. None have increased by more than 6%, with Cumberland County topping the list at 5.09%, closely followed by Centre County at 5.06%. Quite a number of counties have had negative population growth: Cameron County, the least populous in the state, has just 4,683 residents and its population has decreased by 7.69% since the last census, while the larger Cambria County's population has reduced to 134,313, representing a 6.37% decrease.

Name 2021 Population Growth Since 2010 Density (mi²)
Philadelphia County1,585,0103.71%1,784.95
Allegheny County1,213,570-0.85%1,366.66
Montgomery County838,8974.75%944.72
Bucks County629,1860.61%708.56
Delaware County569,7791.93%641.65
Lancaster County549,2345.56%618.52
Chester County530,7956.17%597.75
York County451,4803.69%508.43
Berks County422,4342.52%475.72
Lehigh County371,2366.02%418.07
Westmoreland County345,779-5.27%389.40
Luzerne County316,533-1.39%356.46
Northampton County306,7272.95%345.42
Dauphin County281,1694.80%316.64
Erie County266,096-5.24%299.66
Cumberland County257,8489.31%290.37
Lackawanna County208,484-2.81%234.78
Washington County206,559-0.66%232.62
Butler County188,2832.26%212.03
Monroe County172,2251.40%193.95
Beaver County162,623-4.69%183.14
Centre County161,9535.01%182.38
Franklin County155,9234.00%175.59
Lebanon County142,7016.76%160.70
Schuylkill County140,447-5.29%158.16
Cambria County127,678-11.00%143.78
Fayette County127,176-6.79%143.22
Blair County120,481-5.17%135.68
Lycoming County112,165-3.49%126.31
Mercer County107,330-7.95%120.87
Adams County102,9031.40%115.88
Northumberland County90,369-4.16%101.77
Lawrence County84,280-7.40%94.91
Crawford County83,667-5.58%94.22
Indiana County83,337-6.22%93.85
Clearfield County78,621-3.59%88.54
Somerset County72,597-6.64%81.75
Columbia County64,462-4.30%72.59
Carbon County64,196-1.61%72.29
Armstrong County63,501-7.94%71.51
Bradford County59,381-5.34%66.87
Pike County55,867-2.60%62.91
Wayne County51,293-2.98%57.76
Venango County49,602-9.77%55.86
Bedford County47,476-4.47%53.46
Perry County46,5081.28%52.37
Mifflin County45,992-1.39%51.79
Union County44,735-0.59%50.38
Huntingdon County44,642-2.94%50.27
Jefferson County43,047-4.69%48.48
Tioga County40,393-3.77%45.49
Snyder County40,0800.94%45.14
McKean County39,975-7.77%45.02
Susquehanna County39,864-8.02%44.89
Clinton County38,504-1.93%43.36
Warren County38,471-7.90%43.32
Clarion County37,970-4.89%42.76
Greene County35,377-8.37%39.84
Elk County29,510-7.38%33.23
Wyoming County26,208-7.20%29.51
Juniata County24,8530.92%27.99
Montour County18,210-0.50%20.51
Potter County16,332-6.43%18.39
Fulton County14,540-2.17%16.37
Forest County7,173-6.92%8.08
Sullivan County6,046-5.63%6.81
Cameron County4,339-14.60%4.89