| County | Rank | Change (2020) ↓ | 2025 Pop. | 2020 Pop. |
|---|---|---|---|---|
| Pike County | 1 | 6.85% | 62,589 | 58,574 |
| Cumberland County | 2 | 5.72% | 275,150 | 260,258 |
| Adams County | 3 | 4.36% | 108,326 | 103,798 |
| Chester County | 4 | 3.97% | 556,076 | 534,830 |
| Butler County | 5 | 3.31% | 200,503 | 194,077 |
| York County | 6 | 3.31% | 471,822 | 456,720 |
| Northampton County | 7 | 2.78% | 321,473 | 312,784 |
| Franklin County | 8 | 2.38% | 159,660 | 155,949 |
| Montgomery County | 9 | 2.23% | 876,138 | 856,998 |
| Lancaster County | 10 | 1.74% | 562,447 | 552,821 |
| Lehigh County | 11 | 1.66% | 380,714 | 374,501 |
| Columbia County | 12 | 1.63% | 65,739 | 64,686 |
| Berks County | 13 | 1.55% | 435,317 | 428,671 |
| Schuylkill County | 14 | 1.41% | 144,982 | 142,963 |
| Dauphin County | 15 | 1.26% | 290,328 | 286,710 |
| Luzerne County | 16 | 1.22% | 329,172 | 325,217 |
| Lebanon County | 17 | 1.17% | 144,952 | 143,278 |
| Snyder County | 18 | 1.02% | 40,139 | 39,733 |
| Carbon County | 19 | 0.98% | 65,388 | 64,752 |
| Wayne County | 20 | 0.91% | 51,618 | 51,151 |
| Washington County | 21 | 0.66% | 210,816 | 209,434 |
| Lackawanna County | 22 | 0.62% | 216,869 | 215,539 |
| Perry County | 23 | 0.43% | 46,023 | 45,825 |
| Delaware County | 24 | 0.36% | 578,414 | 576,356 |
| Centre County | 25 | 0.22% | 158,319 | 157,979 |
| Bucks County | 26 | 0.1% | 646,838 | 646,173 |
| Indiana County | 27 | 0% | 83,154 | 83,151 |
| Huntingdon County | 28 | -0.23% | 43,948 | 44,049 |
| Clinton County | 29 | -0.27% | 37,269 | 37,370 |
| Sullivan County | 30 | -0.27% | 5,812 | 5,828 |
| Mifflin County | 31 | -0.73% | 45,798 | 46,137 |
| Bedford County | 32 | -0.76% | 47,208 | 47,568 |
| Susquehanna County | 33 | -0.77% | 38,049 | 38,346 |
| Bradford County | 34 | -0.99% | 59,377 | 59,968 |
| Tioga County | 35 | -1.07% | 40,586 | 41,025 |
| Juniata County | 36 | -1.35% | 23,167 | 23,484 |
| Westmoreland County | 37 | -1.37% | 349,493 | 354,346 |
| Wyoming County | 38 | -1.44% | 25,658 | 26,032 |
| Beaver County | 39 | -1.46% | 165,419 | 167,873 |
| Northumberland County | 40 | -1.56% | 90,114 | 91,545 |
| Lycoming County | 41 | -1.77% | 112,104 | 114,125 |
| Fulton County | 42 | -1.94% | 14,296 | 14,579 |
| Clarion County | 43 | -2% | 36,456 | 37,199 |
| Erie County | 44 | -2.05% | 265,033 | 270,578 |
| Jefferson County | 45 | -2.5% | 43,374 | 44,487 |
| Lawrence County | 46 | -2.53% | 83,792 | 85,970 |
| Blair County | 47 | -2.7% | 119,351 | 122,666 |
| Mercer County | 48 | -3% | 107,235 | 110,550 |
| Monroe County | 49 | -3% | 163,257 | 168,314 |
| Cambria County | 50 | -3.05% | 129,146 | 133,211 |
| Venango County | 51 | -3.06% | 48,825 | 50,365 |
| Crawford County | 52 | -3.12% | 81,193 | 83,807 |
| Allegheny County | 53 | -3.23% | 1,209,265 | 1,249,565 |
| Somerset County | 54 | -3.63% | 71,333 | 74,019 |
| Montour County | 55 | -3.63% | 17,472 | 18,131 |
| McKean County | 56 | -3.66% | 38,919 | 40,399 |
| Warren County | 57 | -3.72% | 37,080 | 38,511 |
| Armstrong County | 58 | -4.06% | 62,814 | 65,470 |
| Elk County | 59 | -4.16% | 29,660 | 30,946 |
| Cameron County | 60 | -4.4% | 4,328 | 4,527 |
| Union County | 61 | -4.46% | 40,746 | 42,646 |
| Potter County | 62 | -4.87% | 15,585 | 16,383 |
| Philadelphia County | 63 | -5.17% | 1,517,954 | 1,600,684 |
| Greene County | 64 | -5.17% | 34,013 | 35,868 |
| Fayette County | 65 | -5.89% | 121,009 | 128,588 |
| Clearfield County | 66 | -5.98% | 75,622 | 80,432 |
| Forest County | 67 | -11.74% | 6,141 | 6,958 |
Pennsylvania's counties show varied growth patterns from 2020 to 2025. Pike County leads with 6.85% annualized growth, followed by Cumberland County (5.72%) and Adams County (4.36%). The largest counties are Philadelphia County (1,517,954), Allegheny County (1,209,265), and Montgomery County (876,138). Of the 67 counties in Pennsylvania, 27 are growing while 40 have experienced population decline. Overall, counties averaged -0.97% annualized growth, with total population growing by -0.42% annually.