| Rank |
County |
Population (2012) |
| 1 |
Philadelphia County, Pennsylvania
|
1,547,607
|
| 2 |
Allegheny County, Pennsylvania
|
1,229,338
|
| 3 |
Montgomery County, Pennsylvania
|
808,460
|
| 4 |
Bucks County, Pennsylvania
|
627,053
|
| 5 |
Delaware County, Pennsylvania
|
561,098
|
| 6 |
Lancaster County, Pennsylvania
|
526,823
|
| 7 |
Chester County, Pennsylvania
|
506,575
|
| 8 |
York County, Pennsylvania
|
437,846
|
| 9 |
Berks County, Pennsylvania
|
413,491
|
| 10 |
Westmoreland County, Pennsylvania
|
363,395
|
| 11 |
Lehigh County, Pennsylvania
|
355,245
|
| 12 |
Luzerne County, Pennsylvania
|
321,027
|
| 13 |
Northampton County, Pennsylvania
|
299,267
|
| 14 |
Erie County, Pennsylvania
|
280,646
|
| 15 |
Dauphin County, Pennsylvania
|
269,665
|
| 16 |
Cumberland County, Pennsylvania
|
238,614
|
| 17 |
Lackawanna County, Pennsylvania
|
214,477
|
| 18 |
Washington County, Pennsylvania
|
208,716
|
| 19 |
Butler County, Pennsylvania
|
184,970
|
| 20 |
Beaver County, Pennsylvania
|
170,245
|
| 21 |
Monroe County, Pennsylvania
|
168,798
|
| 22 |
Centre County, Pennsylvania
|
155,171
|
| 23 |
Franklin County, Pennsylvania
|
151,275
|
| 24 |
Schuylkill County, Pennsylvania
|
147,063
|
| 25 |
Cambria County, Pennsylvania
|
141,584
|
| 26 |
Fayette County, Pennsylvania
|
135,660
|
| 27 |
Lebanon County, Pennsylvania
|
135,251
|
| 28 |
Blair County, Pennsylvania
|
127,121
|
| 29 |
Lycoming County, Pennsylvania
|
117,168
|
| 30 |
Mercer County, Pennsylvania
|
115,655
|
| 31 |
Adams County, Pennsylvania
|
101,482
|
| 32 |
Northumberland County, Pennsylvania
|
94,428
|
| 33 |
Lawrence County, Pennsylvania
|
89,871
|
| 34 |
Indiana County, Pennsylvania
|
88,218
|
| 35 |
Crawford County, Pennsylvania
|
87,598
|
| 36 |
Clearfield County, Pennsylvania
|
81,184
|
| 37 |
Somerset County, Pennsylvania
|
76,957
|
| 38 |
Armstrong County, Pennsylvania
|
68,409
|
| 39 |
Columbia County, Pennsylvania
|
66,887
|
| 40 |
Carbon County, Pennsylvania
|
65,006
|
| 41 |
Bradford County, Pennsylvania
|
62,792
|
| 42 |
Pike County, Pennsylvania
|
56,899
|
| 43 |
Venango County, Pennsylvania
|
54,272
|
| 44 |
Wayne County, Pennsylvania
|
51,955
|
| 45 |
Bedford County, Pennsylvania
|
49,324
|
| 46 |
Mifflin County, Pennsylvania
|
46,773
|
| 47 |
Huntingdon County, Pennsylvania
|
45,943
|
| 48 |
Perry County, Pennsylvania
|
45,701
|
| 49 |
Union County, Pennsylvania
|
44,952
|
| 50 |
Jefferson County, Pennsylvania
|
44,764
|
| 51 |
McKean County, Pennsylvania
|
43,127
|
| 52 |
Susquehanna County, Pennsylvania
|
42,696
|
| 53 |
Tioga County, Pennsylvania
|
42,577
|
| 54 |
Warren County, Pennsylvania
|
41,146
|
| 55 |
Snyder County, Pennsylvania
|
39,672
|
| 56 |
Clarion County, Pennsylvania
|
39,646
|
| 57 |
Clinton County, Pennsylvania
|
39,517
|
| 58 |
Greene County, Pennsylvania
|
38,085
|
| 59 |
Elk County, Pennsylvania
|
31,550
|
| 60 |
Wyoming County, Pennsylvania
|
28,125
|
| 61 |
Juniata County, Pennsylvania
|
24,904
|
| 62 |
Montour County, Pennsylvania
|
18,356
|
| 63 |
Potter County, Pennsylvania
|
17,577
|
| 64 |
Fulton County, Pennsylvania
|
14,772
|
| 65 |
Forest County, Pennsylvania
|
7,667
|
| 66 |
Sullivan County, Pennsylvania
|
6,461
|
| 67 |
Cameron County, Pennsylvania
|
4,939
|