(Links below lead to Quick Facts for Pennsylvania Counties: People, Business & Geography at U.S. Census Bureau.)
| Area | 7/1/2009 | 7/1/2008 | 7/1/2007 | 7/1/2006 | 7/1/2005 | 7/1/2004 | 7/1/2003 | 7/1/2002 | 7/1/2001 | 7/1/2000 | Census 2000 |
| Pennsylvania | 12,604,767 | 12,566,368 | 12,522,531 | 12,471,142 | 12,418,161 | 12,388,368 | 12,357,524 | 12,326,302 | 12,299,533 | 12,285,504 | 12,281,054 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Adams County | 102,323 | 101,943 | 101,241 | 100,465 | 99,081 | 97,718 | 95,841 | 94,242 | 92,821 | 91,594 | 91,292 |
| Allegheny County | 1,218,494 | 1,218,227 | 1,219,922 | 1,223,239 | 1,232,483 | 1,245,875 | 1,257,196 | 1,265,422 | 1,272,519 | 1,279,927 | 1,281,666 |
| Armstrong County | 67,851 | 68,449 | 68,804 | 69,106 | 69,822 | 70,784 | 71,174 | 71,455 | 71,797 | 72,314 | 72,392 |
| Beaver County | 171,673 | 172,396 | 173,015 | 173,928 | 175,372 | 176,877 | 177,887 | 178,611 | 179,598 | 181,113 | 181,412 |
| Bedford County | 49,579 | 49,799 | 49,657 | 49,669 | 49,535 | 49,733 | 49,759 | 49,763 | 49,841 | 50,022 | 49,984 |
| Berks County | 407,125 | 404,771 | 402,476 | 399,279 | 393,788 | 389,177 | 384,547 | 380,629 | 377,155 | 374,521 | 373,638 |
| Blair County | 126,122 | 125,923 | 125,987 | 126,008 | 125,882 | 126,532 | 126,844 | 127,346 | 128,336 | 129,030 | 129,144 |
| Bradford County | 61,131 | 61,209 | 61,347 | 61,441 | 61,747 | 61,803 | 61,952 | 62,326 | 62,496 | 62,760 | 62,761 |
| Bucks County | 626,015 | 623,562 | 621,334 | 619,245 | 616,047 | 613,691 | 610,131 | 607,465 | 603,241 | 599,454 | 597,635 |
| Butler County | 184,694 | 183,663 | 182,488 | 181,676 | 180,074 | 179,405 | 178,664 | 177,504 | 175,847 | 174,519 | 174,083 |
| Cambria County | 143,998 | 144,488 | 145,061 | 145,822 | 146,726 | 147,704 | 148,710 | 149,851 | 150,995 | 152,240 | 152,598 |
| Cameron County | 5,163 | 5,267 | 5,350 | 5,405 | 5,483 | 5,582 | 5,734 | 5,804 | 5,897 | 5,943 | 5,974 |
| Carbon County | 63,865 | 63,623 | 63,163 | 62,098 | 61,532 | 60,645 | 59,991 | 59,549 | 59,201 | 58,826 | 58,802 |
| Centre County | 146,212 | 145,550 | 144,089 | 144,037 | 141,643 | 141,140 | 140,606 | 139,341 | 136,874 | 135,930 | 135,758 |
| Chester County | 498,894 | 493,281 | 487,567 | 480,200 | 471,562 | 463,900 | 455,877 | 448,746 | 441,763 | 435,829 | 433,501 |
| Clarion County | 39,479 | 39,753 | 39,865 | 40,131 | 40,055 | 40,185 | 41,038 | 41,068 | 41,484 | 41,753 | 41,765 |
| Clearfield County | 82,324 | 82,574 | 82,895 | 82,673 | 81,943 | 82,142 | 82,467 | 82,960 | 82,973 | 83,368 | 83,382 |
| Clinton County | 36,797 | 36,992 | 37,125 | 37,230 | 37,169 | 37,227 | 37,384 | 37,521 | 37,706 | 37,915 | 37,914 |
| Columbia County | 65,111 | 65,060 | 64,789 | 64,670 | 64,554 | 64,595 | 64,490 | 64,354 | 64,264 | 64,109 | 64,151 |
| Crawford County | 88,521 | 88,524 | 88,990 | 88,972 | 89,042 | 89,382 | 89,616 | 89,950 | 90,115 | 90,348 | 90,366 |
| Cumberland County | 232,483 | 230,329 | 227,762 | 225,983 | 222,735 | 220,826 | 219,181 | 217,291 | 215,115 | 214,010 | 213,674 |
| Dauphin County | 258,934 | 258,222 | 256,864 | 254,776 | 253,203 | 252,699 | 252,932 | 252,616 | 251,646 | 251,832 | 251,798 |
| Delaware County | 558,028 | 556,251 | 555,019 | 553,664 | 552,126 | 551,681 | 552,355 | 552,588 | 552,663 | 552,092 | 550,864 |
| Elk County | 32,011 | 32,274 | 32,638 | 32,823 | 33,225 | 33,710 | 34,046 | 34,362 | 34,757 | 35,035 | 35,112 |
| Erie County | 280,291 | 279,647 | 279,804 | 279,929 | 278,933 | 279,790 | 282,200 | 281,920 | 281,524 | 280,734 | 280,843 |
| Fayette County | 142,605 | 143,289 | 144,033 | 144,453 | 145,245 | 145,825 | 145,382 | 146,177 | 147,062 | 148,512 | 148,644 |
| Forest County | 6,775 | 6,808 | 6,926 | 7,010 | 6,536 | 5,788 | 4,955 | 4,995 | 5,045 | 4,943 | 4,946 |
| Franklin County | 144,994 | 143,787 | 142,008 | 139,978 | 137,012 | 134,274 | 132,441 | 131,257 | 130,160 | 129,538 | 129,313 |
| Fulton County | 14,852 | 14,938 | 14,936 | 14,742 | 14,571 | 14,506 | 14,435 | 14,277 | 14,193 | 14,258 | 14,261 |
| Greene County | 39,245 | 39,380 | 39,351 | 39,559 | 40,009 | 39,622 | 39,944 | 40,253 | 40,358 | 40,668 | 40,672 |
| Huntingdon County | 45,395 | 45,515 | 45,530 | 45,417 | 45,537 | 45,608 | 45,666 | 45,633 | 45,556 | 45,608 | 45,586 |
| Indiana County | 87,450 | 87,557 | 87,439 | 87,745 | 87,956 | 88,418 | 88,884 | 88,879 | 89,167 | 89,533 | 89,605 |
| Jefferson County | 44,634 | 44,920 | 45,060 | 45,068 | 45,142 | 45,277 | 45,443 | 45,477 | 45,649 | 45,901 | 45,932 |
| Juniata County | 23,118 | 23,095 | 23,080 | 23,096 | 23,146 | 23,105 | 22,932 | 22,817 | 22,729 | 22,840 | 22,821 |
| Lackawanna County | 208,801 | 209,292 | 209,339 | 208,882 | 209,184 | 209,398 | 209,887 | 210,800 | 212,072 | 212,927 | 213,295 |
| Lancaster County | 507,766 | 503,807 | 499,364 | 494,393 | 489,258 | 485,676 | 481,803 | 478,078 | 474,420 | 471,818 | 470,658 |
| Lawrence County | 90,160 | 90,555 | 90,901 | 91,265 | 91,929 | 92,637 | 93,258 | 93,715 | 94,021 | 94,622 | 94,643 |
| Lebanon County | 130,506 | 129,302 | 128,197 | 126,586 | 124,819 | 123,597 | 122,426 | 121,313 | 120,825 | 120,416 | 120,327 |
| Lehigh County | 343,519 | 341,184 | 337,688 | 333,969 | 329,026 | 324,428 | 320,354 | 316,676 | 314,790 | 312,688 | 312,090 |
| Luzerne County | 312,845 | 312,138 | 311,934 | 311,230 | 311,449 | 311,652 | 312,701 | 313,764 | 315,525 | 318,564 | 319,250 |
| Lycoming County | 116,840 | 116,666 | 116,838 | 117,186 | 117,687 | 118,075 | 118,243 | 118,523 | 119,115 | 119,957 | 120,044 |
| McKean County | 43,196 | 43,436 | 43,629 | 43,964 | 43,886 | 44,345 | 44,807 | 45,346 | 45,218 | 45,780 | 45,936 |
| Mercer County | 116,071 | 116,660 | 117,133 | 117,540 | 118,084 | 118,708 | 119,117 | 119,310 | 119,756 | 120,180 | 120,293 |
| Mifflin County | 45,937 | 45,973 | 46,007 | 45,934 | 45,954 | 45,987 | 46,172 | 46,416 | 46,473 | 46,491 | 46,486 |
| Monroe County | 166,355 | 165,540 | 164,670 | 162,891 | 160,169 | 156,762 | 152,999 | 148,277 | 143,560 | 139,771 | 138,687 |
| Montgomery County | 782,339 | 778,452 | 775,631 | 772,968 | 772,142 | 770,700 | 768,240 | 763,218 | 757,879 | 750,975 | 750,097 |
| Montour County | 17,715 | 17,702 | 17,754 | 17,806 | 17,905 | 17,950 | 18,060 | 18,118 | 18,252 | 18,279 | 18,236 |
| Northampton County | 298,990 | 296,965 | 294,817 | 290,971 | 286,309 | 282,227 | 277,232 | 273,141 | 269,429 | 267,465 | 267,066 |
| Northumberland County | 91,311 | 91,220 | 91,148 | 91,190 | 91,561 | 92,057 | 92,585 | 93,063 | 93,534 | 94,472 | 94,556 |
| Perry County | 45,502 | 45,251 | 45,157 | 44,835 | 44,493 | 44,268 | 44,058 | 43,804 | 43,750 | 43,612 | 43,602 |
| Philadelphia County | 1,547,297 | 1,540,351 | 1,530,031 | 1,520,251 | 1,517,628 | 1,514,658 | 1,510,068 | 1,510,550 | 1,512,507 | 1,513,800 | 1,517,550 |
| Pike County | 60,529 | 59,975 | 58,582 | 57,232 | 55,357 | 53,404 | 51,695 | 49,712 | 48,023 | 46,607 | 46,302 |
| Potter County | 16,714 | 16,868 | 17,131 | 17,475 | 17,520 | 17,753 | 17,928 | 18,118 | 18,070 | 18,120 | 18,080 |
| Schuylkill County | 146,952 | 147,154 | 147,226 | 146,959 | 146,059 | 146,389 | 147,281 | 148,458 | 149,110 | 150,086 | 150,336 |
| Snyder County | 38,519 | 38,473 | 38,380 | 38,159 | 37,774 | 37,954 | 37,891 | 37,795 | 37,744 | 37,537 | 37,546 |
| Somerset County | 76,953 | 77,302 | 77,735 | 78,140 | 78,418 | 78,923 | 79,380 | 79,411 | 79,412 | 79,998 | 80,023 |
| Sullivan County | 6,140 | 6,151 | 6,245 | 6,246 | 6,313 | 6,393 | 6,446 | 6,512 | 6,572 | 6,566 | 6,556 |
| Susquehanna County | 40,646 | 40,895 | 41,068 | 41,407 | 41,562 | 41,606 | 41,678 | 41,744 | 42,127 | 42,210 | 42,238 |
| Tioga County | 40,875 | 40,791 | 40,686 | 40,731 | 41,059 | 41,313 | 41,375 | 41,458 | 41,415 | 41,327 | 41,373 |
| Union County | 43,560 | 43,626 | 43,589 | 43,594 | 42,753 | 42,532 | 42,056 | 42,037 | 41,949 | 41,647 | 41,624 |
| Venango County | 54,183 | 54,505 | 54,789 | 55,123 | 55,487 | 55,791 | 56,289 | 56,623 | 57,039 | 57,459 | 57,565 |
| Warren County | 40,638 | 40,776 | 41,003 | 41,153 | 41,554 | 42,155 | 42,523 | 42,966 | 43,526 | 43,785 | 43,863 |
| Washington County | 207,389 | 206,740 | 205,748 | 205,435 | 204,874 | 203,728 | 203,558 | 202,968 | 203,087 | 202,943 | 202,897 |
| Wayne County | 51,337 | 51,268 | 51,837 | 51,602 | 50,123 | 49,272 | 48,837 | 48,292 | 47,992 | 47,893 | 47,722 |
| Westmoreland County | 362,251 | 362,627 | 363,131 | 363,645 | 364,458 | 365,325 | 366,332 | 366,836 | 368,313 | 369,695 | 369,993 |
| Wyoming County | 27,808 | 27,891 | 27,939 | 27,874 | 27,896 | 27,989 | 27,919 | 27,926 | 28,084 | 28,046 | 28,080 |
| York County | 428,937 | 425,766 | 421,589 | 414,969 | 406,555 | 399,490 | 393,622 | 388,885 | 385,397 | 382,749 | 381,751 |
Source: Population Division, U.S. Census Bureau