(Links below lead to Quick Facts for Iowa Counties: People, Business & Geography at U.S. Census Bureau.)
| Area | 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 |
| Iowa | 3,002,555 | 2,983,360 | 2,967,270 | 2,951,775 | 2,942,739 | 2,933,407 | 2,929,395 | 2,929,294 | 2,928,046 | 2,926,324 |
|---|---|---|---|---|---|---|---|---|---|---|
| Adair County | 7,506 | 7,621 | 7,679 | 7,721 | 7,848 | 7,917 | 7,965 | 8,077 | 8,208 | 8,243 |
| Adams County | 4,040 | 4,085 | 4,137 | 4,161 | 4,257 | 4,322 | 4,352 | 4,397 | 4,475 | 4,482 |
| Allamakee County | 14,538 | 14,494 | 14,489 | 14,474 | 14,412 | 14,400 | 14,336 | 14,346 | 14,668 | 14,675 |
| Appanoose County | 12,850 | 12,986 | 13,182 | 13,327 | 13,364 | 13,457 | 13,380 | 13,560 | 13,700 | 13,721 |
| Audubon County | 6,033 | 6,058 | 6,147 | 6,248 | 6,374 | 6,434 | 6,547 | 6,654 | 6,807 | 6,830 |
| Benton County | 26,532 | 26,501 | 26,564 | 26,647 | 26,494 | 26,174 | 25,988 | 25,618 | 25,338 | 25,308 |
| Black Hawk County | 128,347 | 127,204 | 127,005 | 126,549 | 126,243 | 126,090 | 126,622 | 127,624 | 127,997 | 128,012 |
| Boone County | 26,349 | 26,355 | 26,314 | 26,334 | 26,243 | 26,137 | 26,044 | 26,220 | 26,255 | 26,224 |
| Bremer County | 23,690 | 23,723 | 23,583 | 23,420 | 23,388 | 23,283 | 23,206 | 23,403 | 23,282 | 23,325 |
| Buchanan County | 21,032 | 20,903 | 20,844 | 20,757 | 20,849 | 20,774 | 20,758 | 20,942 | 21,078 | 21,093 |
| Buena Vista County | 19,702 | 19,585 | 19,655 | 19,720 | 19,804 | 19,989 | 20,144 | 20,193 | 20,348 | 20,411 |
| Butler County | 14,644 | 14,654 | 14,662 | 14,718 | 14,786 | 14,785 | 14,827 | 15,007 | 15,290 | 15,305 |
| Calhoun County | 9,887 | 9,962 | 10,121 | 10,252 | 10,392 | 10,524 | 10,719 | 10,946 | 11,089 | 11,115 |
| Carroll County | 20,926 | 20,926 | 20,838 | 20,918 | 20,890 | 20,983 | 21,135 | 21,210 | 21,371 | 21,421 |
| Cass County | 13,840 | 13,855 | 13,895 | 13,916 | 14,075 | 14,225 | 14,211 | 14,473 | 14,671 | 14,684 |
| Cedar County | 18,079 | 17,963 | 17,981 | 17,944 | 18,037 | 18,063 | 18,052 | 18,076 | 18,200 | 18,187 |
| Cerro Gordo County | 43,786 | 44,004 | 44,128 | 44,341 | 44,664 | 45,146 | 45,264 | 45,741 | 46,351 | 46,447 |
| Cherokee County | 11,552 | 11,679 | 11,823 | 12,030 | 12,218 | 12,352 | 12,534 | 12,839 | 13,006 | 13,035 |
| Chickasaw County | 12,121 | 12,184 | 12,281 | 12,280 | 12,448 | 12,560 | 12,772 | 13,052 | 13,064 | 13,095 |
| Clarke County | 9,032 | 8,979 | 9,061 | 9,084 | 9,228 | 9,217 | 9,172 | 9,181 | 9,187 | 9,133 |
| Clay County | 16,691 | 16,686 | 16,733 | 16,777 | 16,908 | 16,949 | 17,062 | 17,249 | 17,370 | 17,372 |
| Clayton County | 17,566 | 17,672 | 17,775 | 17,876 | 18,043 | 18,119 | 18,218 | 18,454 | 18,607 | 18,678 |
| Clinton County | 48,942 | 49,056 | 49,183 | 49,268 | 49,358 | 49,471 | 49,600 | 49,841 | 50,048 | 50,149 |
| Crawford County | 16,415 | 16,516 | 16,482 | 16,554 | 16,642 | 16,724 | 16,826 | 16,878 | 16,925 | 16,942 |
| Dallas County | 59,930 | 57,201 | 54,612 | 51,796 | 49,400 | 46,317 | 44,331 | 42,721 | 41,069 | 40,750 |
| Davis County | 8,569 | 8,560 | 8,531 | 8,514 | 8,561 | 8,498 | 8,566 | 8,571 | 8,542 | 8,541 |
| Decatur County | 8,409 | 8,432 | 8,402 | 8,472 | 8,465 | 8,478 | 8,550 | 8,656 | 8,659 | 8,689 |
| Delaware County | 17,301 | 17,450 | 17,511 | 17,622 | 17,798 | 17,978 | 18,123 | 18,212 | 18,388 | 18,404 |
| Des Moines County | 40,629 | 40,587 | 40,459 | 40,540 | 40,725 | 41,132 | 41,305 | 41,916 | 42,285 | 42,351 |
| Dickinson County | 16,775 | 16,669 | 16,668 | 16,610 | 16,480 | 16,322 | 16,348 | 16,476 | 16,461 | 16,424 |
| Dubuque County | 92,724 | 92,296 | 91,398 | 90,975 | 90,633 | 90,109 | 89,205 | 88,988 | 89,231 | 89,143 |
| Emmet County | 10,457 | 10,397 | 10,417 | 10,476 | 10,513 | 10,687 | 10,799 | 10,875 | 10,992 | 11,027 |
| Fayette County | 20,273 | 20,397 | 20,701 | 20,954 | 21,034 | 21,305 | 21,429 | 21,675 | 21,992 | 22,008 |
| Floyd County | 16,183 | 16,269 | 16,339 | 16,311 | 16,420 | 16,512 | 16,587 | 16,618 | 16,854 | 16,900 |
| Franklin County | 10,477 | 10,548 | 10,497 | 10,610 | 10,607 | 10,568 | 10,633 | 10,603 | 10,685 | 10,704 |
| Fremont County | 7,446 | 7,553 | 7,565 | 7,570 | 7,618 | 7,714 | 7,772 | 7,869 | 7,996 | 8,010 |
| Greene County | 9,293 | 9,479 | 9,569 | 9,795 | 9,941 | 10,009 | 10,100 | 10,145 | 10,338 | 10,366 |
| Grundy County | 12,183 | 12,147 | 12,237 | 12,238 | 12,249 | 12,243 | 12,305 | 12,287 | 12,362 | 12,369 |
| Guthrie County | 10,956 | 11,015 | 11,066 | 11,214 | 11,361 | 11,319 | 11,221 | 11,222 | 11,342 | 11,353 |
| Hamilton County | 15,357 | 15,558 | 15,762 | 15,937 | 16,023 | 16,161 | 16,212 | 16,168 | 16,413 | 16,438 |
| Hancock County | 11,354 | 11,368 | 11,546 | 11,624 | 11,671 | 11,772 | 11,761 | 11,904 | 12,096 | 12,100 |
| Hardin County | 17,371 | 17,473 | 17,616 | 17,775 | 18,008 | 18,217 | 18,424 | 18,650 | 18,816 | 18,812 |
| Harrison County | 15,222 | 15,403 | 15,507 | 15,530 | 15,549 | 15,549 | 15,499 | 15,639 | 15,691 | 15,666 |
| Henry County | 20,213 | 20,173 | 20,101 | 20,167 | 20,074 | 20,106 | 19,969 | 20,337 | 20,292 | 20,336 |
| Howard County | 9,484 | 9,516 | 9,540 | 9,624 | 9,682 | 9,715 | 9,796 | 9,868 | 9,914 | 9,932 |
| Humboldt County | 9,514 | 9,578 | 9,732 | 9,810 | 9,944 | 10,020 | 10,078 | 10,282 | 10,369 | 10,381 |
| Ida County | 6,862 | 6,930 | 6,989 | 7,169 | 7,295 | 7,444 | 7,547 | 7,659 | 7,796 | 7,837 |
| Iowa County | 15,877 | 15,860 | 15,957 | 15,925 | 15,812 | 15,836 | 15,762 | 15,784 | 15,708 | 15,671 |
| Jackson County | 19,965 | 20,018 | 20,058 | 20,051 | 20,090 | 20,107 | 20,122 | 20,255 | 20,302 | 20,296 |
| Jasper County | 36,583 | 36,647 | 36,816 | 37,028 | 37,266 | 37,406 | 37,369 | 37,269 | 37,215 | 37,213 |
| Jefferson County | 15,463 | 15,551 | 15,501 | 15,560 | 15,688 | 15,723 | 15,804 | 16,034 | 16,156 | 16,181 |
| Johnson County | 128,094 | 125,454 | 123,126 | 121,236 | 119,764 | 117,460 | 115,534 | 113,849 | 111,461 | 111,006 |
| Jones County | 20,346 | 20,350 | 20,331 | 20,313 | 20,373 | 20,217 | 20,152 | 20,159 | 20,209 | 20,221 |
| Keokuk County | 10,697 | 10,750 | 10,774 | 10,899 | 11,079 | 11,198 | 11,344 | 11,374 | 11,418 | 11,400 |
| Kossuth County | 15,463 | 15,590 | 15,710 | 15,949 | 16,151 | 16,290 | 16,496 | 16,779 | 17,124 | 17,163 |
| Lee County | 35,408 | 35,706 | 35,877 | 36,125 | 36,394 | 36,473 | 36,855 | 37,381 | 37,918 | 38,052 |
| Linn County | 208,574 | 205,621 | 202,488 | 200,191 | 198,139 | 196,707 | 195,893 | 194,295 | 192,288 | 191,701 |
| Louisa County | 11,725 | 11,768 | 11,766 | 11,775 | 12,049 | 12,176 | 12,195 | 12,167 | 12,168 | 12,183 |
| Lucas County | 9,290 | 9,433 | 9,460 | 9,592 | 9,623 | 9,474 | 9,439 | 9,443 | 9,405 | 9,422 |
| Lyon County | 11,234 | 11,247 | 11,366 | 11,467 | 11,526 | 11,569 | 11,589 | 11,637 | 11,741 | 11,763 |
| Madison County | 15,507 | 15,377 | 15,194 | 14,870 | 14,693 | 14,457 | 14,317 | 14,150 | 14,058 | 14,019 |
| Mahaska County | 22,321 | 22,253 | 22,153 | 22,233 | 22,069 | 22,026 | 22,311 | 22,377 | 22,304 | 22,335 |
| Marion County | 32,571 | 32,489 | 32,728 | 32,321 | 32,263 | 32,279 | 32,411 | 32,506 | 32,102 | 32,052 |
| Marshall County | 39,523 | 39,214 | 38,934 | 39,066 | 39,251 | 39,040 | 39,026 | 39,263 | 39,313 | 39,311 |
| Mills County | 15,113 | 15,123 | 15,117 | 14,853 | 14,701 | 14,600 | 14,535 | 14,482 | 14,555 | 14,547 |
| Mitchell County | 10,710 | 10,745 | 10,781 | 10,791 | 10,896 | 10,831 | 10,828 | 10,739 | 10,867 | 10,874 |
| Monona County | 8,966 | 9,071 | 9,181 | 9,348 | 9,514 | 9,685 | 9,706 | 9,819 | 10,003 | 10,020 |
| Monroe County | 7,577 | 7,583 | 7,644 | 7,722 | 7,778 | 7,805 | 7,788 | 7,934 | 8,000 | 8,016 |
| Montgomery County | 10,870 | 10,978 | 11,137 | 11,179 | 11,163 | 11,190 | 11,302 | 11,508 | 11,792 | 11,771 |
| Muscatine County | 42,504 | 42,335 | 42,190 | 41,968 | 41,810 | 41,674 | 41,796 | 41,786 | 41,796 | 41,722 |
| O'Brien County | 13,952 | 14,060 | 14,184 | 14,249 | 14,340 | 14,587 | 14,683 | 14,881 | 15,066 | 15,102 |
| Osceola County | 6,444 | 6,451 | 6,581 | 6,633 | 6,773 | 6,818 | 6,853 | 6,939 | 6,982 | 7,003 |
| Page County | 15,664 | 15,896 | 16,046 | 16,007 | 16,002 | 16,166 | 16,425 | 16,869 | 16,917 | 16,976 |
| Palo Alto County | 9,345 | 9,427 | 9,455 | 9,586 | 9,660 | 9,670 | 9,845 | 10,029 | 10,136 | 10,147 |
| Plymouth County | 24,323 | 24,338 | 24,485 | 24,577 | 24,709 | 24,597 | 24,562 | 24,749 | 24,851 | 24,849 |
| Pocahontas County | 7,560 | 7,666 | 7,685 | 7,804 | 7,978 | 8,150 | 8,341 | 8,461 | 8,600 | 8,662 |
| Polk County | 424,778 | 417,668 | 410,089 | 402,762 | 394,352 | 390,308 | 385,879 | 381,062 | 375,925 | 374,601 |
| Pottawattamie County | 89,647 | 89,355 | 89,284 | 88,981 | 88,784 | 88,044 | 87,933 | 87,662 | 87,965 | 87,704 |
| Poweshiek County | 18,590 | 18,713 | 18,670 | 18,643 | 18,805 | 18,809 | 18,756 | 18,850 | 18,834 | 18,815 |
| Ringgold County | 5,156 | 5,141 | 5,142 | 5,193 | 5,248 | 5,264 | 5,294 | 5,390 | 5,461 | 5,469 |
| Sac County | 10,311 | 10,360 | 10,528 | 10,540 | 10,725 | 10,852 | 11,042 | 11,359 | 11,474 | 11,529 |
| Scott County | 164,690 | 162,445 | 161,476 | 160,101 | 159,307 | 158,758 | 158,622 | 158,501 | 158,663 | 158,668 |
| Shelby County | 12,131 | 12,310 | 12,305 | 12,419 | 12,657 | 12,754 | 12,844 | 12,995 | 13,070 | 13,173 |
| Sioux County | 32,200 | 32,044 | 32,118 | 31,909 | 31,867 | 31,780 | 31,792 | 31,738 | 31,557 | 31,589 |
| Story County | 86,754 | 85,306 | 83,505 | 81,852 | 81,957 | 81,481 | 81,607 | 80,052 | 80,121 | 79,981 |
| Tama County | 17,690 | 17,767 | 17,828 | 17,910 | 17,938 | 17,850 | 17,903 | 18,013 | 18,072 | 18,103 |
| Taylor County | 6,298 | 6,391 | 6,512 | 6,537 | 6,692 | 6,750 | 6,822 | 6,898 | 6,978 | 6,958 |
| Union County | 12,261 | 12,156 | 12,059 | 11,951 | 11,925 | 11,885 | 12,084 | 12,202 | 12,272 | 12,309 |
| Van Buren County | 7,676 | 7,672 | 7,663 | 7,628 | 7,666 | 7,673 | 7,737 | 7,736 | 7,817 | 7,809 |
| Wapello County | 35,513 | 35,459 | 35,718 | 35,785 | 35,660 | 35,720 | 35,802 | 35,952 | 36,006 | 36,051 |
| Warren County | 45,059 | 44,408 | 43,698 | 42,962 | 42,294 | 41,963 | 41,296 | 41,017 | 40,779 | 40,671 |
| Washington County | 21,343 | 21,236 | 21,162 | 21,057 | 21,029 | 21,008 | 20,993 | 21,005 | 20,701 | 20,670 |
| Wayne County | 6,253 | 6,269 | 6,374 | 6,428 | 6,508 | 6,573 | 6,640 | 6,642 | 6,725 | 6,730 |
| Webster County | 38,517 | 38,606 | 38,635 | 38,579 | 38,932 | 39,368 | 39,667 | 40,036 | 40,196 | 40,235 |
| Winnebago County | 10,901 | 10,927 | 11,011 | 11,203 | 11,211 | 11,317 | 11,336 | 11,535 | 11,743 | 11,723 |
| Winneshiek County | 20,913 | 20,888 | 20,847 | 20,886 | 20,906 | 20,903 | 21,127 | 21,238 | 21,285 | 21,310 |
| Woodbury County | 102,559 | 101,910 | 101,796 | 101,388 | 102,456 | 102,517 | 103,019 | 103,313 | 103,816 | 103,877 |
| Worth County | 7,661 | 7,657 | 7,653 | 7,721 | 7,713 | 7,722 | 7,797 | 7,802 | 7,901 | 7,909 |
| Wright County | 12,903 | 13,021 | 13,145 | 13,373 | 13,537 | 13,627 | 13,826 | 14,056 | 14,312 | 14,334 |
Source: Population Division, U.S. Census Bureau