1850
| RANK | COUNTY | TOTAL POPULATION | RANK | COUNTY | TOTAL POPULATION | |
| 1 | Philadelphia County | 408,762 | 31 | Adams County | 25,981 | |
| 2 | Allegheny County | 138,290 | 2 | Allegheny County | 138,290 | |
| 3 | Lancaster County | 98,944 | 24 | Armstrong County | 29,560 | |
| 4 | Berks County | 77,129 | 27 | Beaver County | 26,689 | |
| 5 | Chester County | 66,438 | 39 | Bedford County | 23,052 | |
| 6 | Schuylkill County | 60,713 | 4 | Berks County | 77,129 | |
| 7 | Montgomery County | 58,291 | 42 | Blair County | 21,777 | |
| 8 | York County | 57,450 | 13 | Bradford County | 42,831 | |
| 9 | Bucks County | 56,091 | 9 | Bucks County | 56,091 | |
| 10 | Luzerne County | 56,072 | 23 | Butler County | 30,346 | |
| 11 | Westmoreland County | 51,726 | 46 | Cambria County | 17,773 | |
| 12 | Washington County | 44,939 | 48 | Carbon County | 15,686 | |
| 13 | Bradford County | 42,831 | 37 | Centre County | 23,355 | |
| 14 | Northampton County | 40,235 | 5 | Chester County | 66,438 | |
| 15 | Franklin County | 39,904 | 36 | Clarion County | 23,565 | |
| 16 | Fayette County | 39,112 | 55 | Clearfield County | 12,586 | |
| 17 | Erie County | 38,742 | 56 | Clinton County | 11,207 | |
| 18 | Crawford County | 37,849 | 47 | Columbia County | 17,710 | |
| 19 | Dauphin County | 35,754 | 18 | Crawford County | 37,849 | |
| 20 | Cumberland County | 34,327 | 20 | Cumberland County | 34,327 | |
| 21 | Mercer County | 33,172 | 19 | Dauphin County | 35,754 | |
| 22 | Lehigh County | 32,479 | 33 | Delaware County | 24,679 | |
| 23 | Butler County | 30,346 | 63 | Elk County | 3,531 | |
| 24 | Armstrong County | 29,560 | 17 | Erie County | 38,742 | |
| 25 | Susquehanna County | 28,688 | 16 | Fayette County | 39,112 | |
| 26 | Indiana County | 27,170 | 15 | Franklin County | 39,904 | |
| 27 | Beaver County | 26,689 | 58 | Fulton County | 7,567 | |
| 28 | Lycoming County | 26,257 | 40 | Greene County | 22,136 | |
| 29 | Union County | 26,083 | 32 | Huntingdon County | 24,786 | |
| 30 | Lebanon County | 26,071 | 26 | Indiana County | 27,170 | |
| 31 | Adams County | 25,981 | 51 | Jefferson County | 13,518 | |
| 32 | Huntingdon County | 24,786 | 54 | Juniata County | 13,029 | |
| 33 | Delaware County | 24,679 | 3 | Lancaster County | 98,944 | |
| 34 | Somerset County | 24,416 | 43 | Lawrence County | 21,079 | |
| 35 | Tioga County | 23,987 | 30 | Lebanon County | 26,071 | |
| 36 | Clarion County | 23,565 | 22 | Lehigh County | 32,479 | |
| 37 | Centre County | 23,355 | 10 | Luzerne County | 56,072 | |
| 38 | Northumberland County | 23,272 | 28 | Lycoming County | 26,257 | |
| 39 | Bedford County | 23,052 | 61 | McKean County | 5,254 | |
| 40 | Greene County | 22,136 | 21 | Mercer County | 33,172 | |
| 41 | Wayne County | 21,890 | 49 | Mifflin County | 14,980 | |
| 42 | Blair County | 21,777 | 52 | Monroe County | 13,270 | |
| 43 | Lawrence County | 21,079 | 7 | Montgomery County | 58,291 | |
| 44 | Perry County | 20,088 | 53 | Montour County | 13,239 | |
| 45 | Venango County | 18,310 | 14 | Northampton County | 40,235 | |
| 46 | Cambria County | 17,773 | 38 | Northumberland County | 23,272 | |
| 47 | Columbia County | 17,710 | 44 | Perry County | 20,088 | |
| 48 | Carbon County | 15,686 | 1 | Philadelphia County | 408,762 | |
| 49 | Mifflin County | 14,980 | 60 | Pike County | 5,881 | |
| 50 | Warren County |