| County | Rank | Change (2020) ↓ | 2026 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Pike County | 1 | 8.12% | 63,352 | 58,593 |
| Cumberland County | 2 | 7.54% | 279,884 | 260,251 |
| Chester County | 3 | 4.64% | 559,702 | 534,858 |
| York County | 4 | 4.31% | 476,408 | 456,725 |
| Northampton County | 5 | 4.13% | 325,737 | 312,809 |
| Adams County | 6 | 4.06% | 108,033 | 103,814 |
| Franklin County | 7 | 3.78% | 161,828 | 155,938 |
| Butler County | 8 | 3.61% | 201,038 | 194,026 |
| Berks County | 9 | 3.06% | 441,765 | 428,651 |
| Lehigh County | 10 | 3.04% | 385,827 | 374,449 |
| Lebanon County | 11 | 2.86% | 147,368 | 143,272 |
| Montgomery County | 12 | 2.72% | 880,126 | 856,829 |
| Perry County | 13 | 2.65% | 47,046 | 45,830 |
| Columbia County | 14 | 2.64% | 66,389 | 64,681 |
| Luzerne County | 15 | 2.51% | 333,354 | 325,195 |
| Dauphin County | 16 | 2.47% | 293,785 | 286,694 |
| Lancaster County | 17 | 2.07% | 564,256 | 552,819 |
| Schuylkill County | 18 | 1.97% | 145,761 | 142,944 |
| Carbon County | 19 | 1.95% | 66,027 | 64,765 |
| Wayne County | 20 | 1.75% | 52,044 | 51,151 |
| Clinton County | 21 | 1.48% | 37,933 | 37,381 |
| Washington County | 22 | 0.74% | 210,969 | 209,413 |
| Delaware County | 23 | 0.69% | 580,458 | 576,505 |
| Lackawanna County | 24 | 0.49% | 216,586 | 215,529 |
| Mifflin County | 25 | 0.19% | 46,231 | 46,144 |
| Bucks County | 26 | 0.16% | 647,240 | 646,212 |
| Sullivan County | 27 | -0.1% | 5,817 | 5,823 |
| Susquehanna County | 28 | -0.16% | 38,294 | 38,355 |
| Snyder County | 29 | -0.29% | 39,621 | 39,737 |
| Bedford County | 30 | -0.37% | 47,394 | 47,569 |
| Monroe County | 31 | -0.46% | 167,540 | 168,310 |
| Juniata County | 32 | -0.53% | 23,352 | 23,476 |
| Bradford County | 33 | -0.61% | 59,607 | 59,975 |
| Fulton County | 34 | -0.7% | 14,476 | 14,578 |
| Indiana County | 35 | -0.79% | 82,499 | 83,158 |
| Beaver County | 36 | -0.93% | 166,295 | 167,857 |
| Centre County | 37 | -1.11% | 156,281 | 158,035 |
| Wyoming County | 38 | -1.19% | 25,723 | 26,033 |
| Tioga County | 39 | -1.42% | 40,441 | 41,025 |
| Philadelphia County | 40 | -1.56% | 1,575,827 | 1,600,737 |
| Clarion County | 41 | -1.56% | 36,619 | 37,200 |
| Union County | 42 | -1.58% | 41,985 | 42,659 |
| Montour County | 43 | -1.62% | 17,836 | 18,130 |
| Lycoming County | 44 | -1.63% | 112,256 | 114,120 |
| Westmoreland County | 45 | -1.72% | 348,175 | 354,270 |
| Northumberland County | 46 | -1.83% | 89,871 | 91,544 |
| Erie County | 47 | -2.03% | 265,229 | 270,724 |
| Allegheny County | 48 | -2.14% | 1,222,896 | 1,249,585 |
| Venango County | 49 | -2.37% | 49,174 | 50,370 |
| Crawford County | 50 | -2.58% | 81,638 | 83,797 |
| Lawrence County | 51 | -2.59% | 83,735 | 85,961 |
| Mercer County | 52 | -2.78% | 107,482 | 110,553 |
| Armstrong County | 53 | -2.83% | 63,641 | 65,496 |
| Clearfield County | 54 | -2.93% | 78,069 | 80,427 |
| Jefferson County | 55 | -2.96% | 43,170 | 44,488 |
| Blair County | 56 | -2.96% | 119,031 | 122,667 |
| Somerset County | 57 | -2.97% | 71,799 | 73,994 |
| Huntingdon County | 58 | -3.24% | 42,618 | 44,043 |
| Potter County | 59 | -3.69% | 15,784 | 16,389 |
| Elk County | 60 | -3.73% | 29,785 | 30,940 |
| Cambria County | 61 | -3.88% | 128,031 | 133,200 |
| McKean County | 62 | -4.27% | 38,679 | 40,405 |
| Warren County | 63 | -4.54% | 36,765 | 38,513 |
| Forest County | 64 | -4.86% | 6,633 | 6,972 |
| Fayette County | 65 | -5.06% | 122,083 | 128,585 |
| Greene County | 66 | -6.25% | 33,628 | 35,869 |
| Cameron County | 67 | -9.69% | 4,090 | 4,529 |
Pennsylvania's counties show varied growth patterns from 2020 to 2026. Pike County leads with 1.31% annualized growth, followed by Cumberland County (1.22%) and Chester County (0.76%). The largest counties are Philadelphia County (1,575,827), Allegheny County (1,222,896), and Montgomery County (880,126). Of the 67 counties in Pennsylvania, 26 are growing while 41 have experienced population decline. Overall, counties averaged -0.07% annualized growth, with total population growing by 0.1% annually.
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