(Links below lead to Quick Facts for Montana 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 |
| Montana | 967,440 | 956,624 | 945,428 | 934,888 | 925,969 | 916,754 | 909,859 | 905,854 | 903,283 | 902,195 |
|---|---|---|---|---|---|---|---|---|---|---|
| Beaverhead County | 8,903 | 8,807 | 8,835 | 8,764 | 8,812 | 8,840 | 8,959 | 9,018 | 9,191 | 9,202 |
| Big Horn County | 12,841 | 12,765 | 12,681 | 12,764 | 12,842 | 12,733 | 12,773 | 12,806 | 12,659 | 12,671 |
| Blaine County | 6,491 | 6,524 | 6,556 | 6,613 | 6,591 | 6,715 | 6,786 | 6,757 | 6,977 | 7,009 |
| Broadwater County | 4,704 | 4,579 | 4,491 | 4,432 | 4,438 | 4,361 | 4,343 | 4,365 | 4,366 | 4,385 |
| Carbon County | 9,657 | 9,709 | 9,687 | 9,746 | 9,662 | 9,646 | 9,651 | 9,635 | 9,564 | 9,552 |
| Carter County | 1,234 | 1,262 | 1,266 | 1,273 | 1,299 | 1,304 | 1,333 | 1,350 | 1,345 | 1,360 |
| Cascade County | 82,026 | 81,784 | 81,854 | 81,791 | 81,690 | 81,059 | 80,590 | 80,380 | 80,200 | 80,357 |
| Chouteau County | 5,225 | 5,245 | 5,259 | 5,308 | 5,394 | 5,499 | 5,598 | 5,750 | 5,975 | 5,970 |
| Custer County | 11,149 | 11,165 | 11,084 | 11,167 | 11,305 | 11,278 | 11,405 | 11,426 | 11,667 | 11,696 |
| Daniels County | 1,643 | 1,645 | 1,701 | 1,765 | 1,793 | 1,875 | 1,911 | 2,003 | 2,012 | 2,017 |
| Dawson County | 8,490 | 8,554 | 8,543 | 8,544 | 8,558 | 8,649 | 8,694 | 8,903 | 9,036 | 9,059 |
| Deer Lodge County | 8,843 | 8,838 | 8,828 | 8,990 | 9,002 | 8,981 | 9,094 | 9,221 | 9,385 | 9,417 |
| Fallon County | 2,716 | 2,690 | 2,637 | 2,625 | 2,703 | 2,714 | 2,688 | 2,719 | 2,811 | 2,837 |
| Fergus County | 11,195 | 11,165 | 11,219 | 11,219 | 11,362 | 11,422 | 11,568 | 11,675 | 11,880 | 11,893 |
| Flathead County | 88,473 | 86,766 | 84,549 | 82,530 | 80,626 | 79,152 | 77,269 | 75,987 | 74,710 | 74,471 |
| Gallatin County | 89,824 | 87,243 | 84,370 | 80,671 | 77,408 | 74,689 | 71,967 | 70,170 | 68,358 | 67,831 |
| Garfield County | 1,184 | 1,205 | 1,201 | 1,173 | 1,211 | 1,234 | 1,245 | 1,262 | 1,267 | 1,279 |
| Glacier County | 13,297 | 13,334 | 13,396 | 13,410 | 13,511 | 13,254 | 13,164 | 13,138 | 13,197 | 13,247 |
| Golden Valley County | 1,081 | 1,118 | 1,102 | 1,113 | 1,081 | 1,040 | 1,054 | 1,015 | 1,023 | 1,042 |
| Granite County | 2,821 | 2,841 | 2,876 | 2,896 | 2,852 | 2,862 | 2,873 | 2,879 | 2,843 | 2,830 |
| Hill County | 16,454 | 16,536 | 16,431 | 16,211 | 16,215 | 16,202 | 16,297 | 16,467 | 16,628 | 16,673 |
| Jefferson County | 11,255 | 11,090 | 10,857 | 10,779 | 10,574 | 10,312 | 10,226 | 10,120 | 10,077 | 10,049 |
| Judith Basin County | 2,014 | 2,040 | 2,121 | 2,135 | 2,176 | 2,184 | 2,238 | 2,263 | 2,332 | 2,329 |
| Lake County | 28,690 | 28,395 | 28,343 | 27,969 | 27,606 | 27,106 | 26,835 | 26,843 | 26,624 | 26,507 |
| Lewis and Clark County | 60,925 | 59,929 | 58,898 | 58,095 | 57,707 | 56,866 | 56,127 | 56,191 | 55,881 | 55,716 |
| Liberty County | 1,725 | 1,797 | 1,842 | 1,938 | 1,997 | 2,009 | 2,006 | 2,089 | 2,153 | 2,158 |
| Lincoln County | 18,971 | 18,848 | 18,637 | 18,687 | 18,602 | 18,569 | 18,480 | 18,548 | 18,812 | 18,837 |
| Madison County | 7,509 | 7,405 | 7,185 | 7,088 | 6,902 | 6,823 | 6,889 | 6,834 | 6,873 | 6,851 |
| McCone County | 1,676 | 1,716 | 1,720 | 1,746 | 1,757 | 1,780 | 1,819 | 1,873 | 1,965 | 1,977 |
| Meagher County | 1,868 | 1,894 | 1,913 | 1,908 | 1,950 | 1,926 | 1,910 | 1,921 | 1,929 | 1,932 |
| Mineral County | 3,862 | 3,872 | 3,955 | 3,944 | 3,846 | 3,837 | 3,781 | 3,815 | 3,888 | 3,884 |
| Missoula County | 107,320 | 105,638 | 103,973 | 102,140 | 100,810 | 99,854 | 98,925 | 97,398 | 96,167 | 95,802 |
| Musselshell County | 4,498 | 4,470 | 4,462 | 4,379 | 4,419 | 4,401 | 4,389 | 4,397 | 4,492 | 4,497 |
| Park County | 16,189 | 16,072 | 15,845 | 15,750 | 15,616 | 15,623 | 15,746 | 15,691 | 15,720 | 15,694 |
| Petroleum County | 436 | 433 | 461 | 460 | 491 | 484 | 492 | 483 | 492 | 493 |
| Phillips County | 3,904 | 3,934 | 3,953 | 4,044 | 4,143 | 4,197 | 4,300 | 4,444 | 4,548 | 4,601 |
| Pondera County | 5,852 | 5,921 | 5,937 | 5,976 | 6,003 | 6,125 | 6,220 | 6,326 | 6,377 | 6,424 |
| Powder River County | 1,694 | 1,698 | 1,736 | 1,700 | 1,760 | 1,815 | 1,822 | 1,813 | 1,856 | 1,858 |
| Powell County | 7,041 | 7,115 | 7,100 | 6,946 | 6,839 | 6,860 | 6,958 | 7,011 | 7,178 | 7,180 |
| Prairie County | 1,064 | 1,043 | 1,059 | 1,077 | 1,139 | 1,157 | 1,169 | 1,209 | 1,185 | 1,199 |
| Ravalli County | 40,664 | 40,331 | 39,817 | 39,229 | 38,920 | 38,315 | 37,409 | 36,740 | 36,307 | 36,070 |
| Richland County | 9,270 | 9,171 | 9,080 | 9,021 | 8,950 | 9,080 | 9,212 | 9,384 | 9,613 | 9,667 |
| Roosevelt County | 10,089 | 10,134 | 10,240 | 10,405 | 10,432 | 10,320 | 10,372 | 10,540 | 10,605 | 10,620 |
| Rosebud County | 9,190 | 9,161 | 9,095 | 9,141 | 9,146 | 9,214 | 9,203 | 9,248 | 9,388 | 9,383 |
| Sanders County | 11,034 | 11,011 | 10,877 | 10,728 | 10,675 | 10,384 | 10,346 | 10,405 | 10,246 | 10,227 |
| Sheridan County | 3,283 | 3,365 | 3,401 | 3,480 | 3,605 | 3,635 | 3,782 | 3,926 | 4,073 | 4,105 |
| Silver Bow County | 32,803 | 32,602 | 32,644 | 32,755 | 32,879 | 33,053 | 33,348 | 33,711 | 34,515 | 34,606 |
| Stillwater County | 8,687 | 8,630 | 8,472 | 8,319 | 8,303 | 8,342 | 8,361 | 8,337 | 8,215 | 8,195 |
| Sweet Grass County | 3,790 | 3,794 | 3,688 | 3,638 | 3,651 | 3,575 | 3,613 | 3,596 | 3,639 | 3,609 |
| Teton County | 5,992 | 6,006 | 6,013 | 6,074 | 6,196 | 6,311 | 6,290 | 6,379 | 6,435 | 6,445 |
| Toole County | 5,141 | 5,162 | 5,133 | 5,198 | 5,068 | 5,024 | 5,271 | 5,277 | 5,262 | 5,267 |
| Treasure County | 637 | 648 | 676 | 698 | 741 | 742 | 765 | 821 | 854 | 861 |
| Valley County | 6,892 | 6,884 | 6,907 | 7,038 | 7,155 | 7,221 | 7,370 | 7,507 | 7,638 | 7,675 |
| Wheatland County | 2,010 | 1,982 | 1,965 | 2,032 | 2,073 | 2,102 | 2,176 | 2,171 | 2,251 | 2,259 |
| Wibaux County | 866 | 892 | 886 | 919 | 956 | 971 | 997 | 1,016 | 1,071 | 1,068 |
| Yellowstone County | 142,348 | 139,766 | 137,971 | 136,447 | 134,527 | 133,028 | 131,750 | 130,601 | 129,528 | 129,352 |
Source: Population Division, U.S. Census Bureau