| County | 1990 | 1980 | 1970 | 1960 | 1950 | 1940 | 1930 | 1920 | 1910 | 1900 | 1890 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| WASHINGTON | 4,866,692 | 4,132,156 | 3,409,169 | 2,853,214 | 2,378,963 | 1,736,191 | 1,563,396 | 1,356,621 | 1,141,990 | 518,103 | 357,232 |
| Adams | 13,603 | 13,267 | 12,014 | 9,929 | 6,584 | 6,209 | 7,719 | 9,623 | 10,920 | 4,840 | 2,098 |
| Asotin | 17,605 | 16,823 | 13,799 | 12,909 | 10,878 | 8,365 | 8,136 | 6,539 | 5,831 | 3,366 | 1,580 |
| Benton | 112,560 | 109,444 | 67,540 | 62,070 | 51,370 | 12,053 | 10,952 | 10,903 | 7,937 | --- | --- |
| Chelan | 52,250 | 45,061 | 41,355 | 40,744 | 39,301 | 34,412 | 31,634 | 20,906 | 15,104 | 3,931 | --- |
| Clallam | 56,464 | 51,648 | 34,770 | 30,022 | 26,396 | 21,848 | 20,449 | 11,368 | 6,755 | 5,603 | 2,771 |
| Clark | 238,053 | 192,227 | 128,454 | 93,809 | 85,307 | 49,852 | 40,316 | 32,805 | 26,115 | 13,419 | 11,709 |
| Columbia | 4,024 | 4,057 | 4,439 | 4,569 | 4,860 | 5,549 | 5,325 | 6,093 | 7,042 | 7,128 | 6,709 |
| Cowlitz | 82,119 | 79,548 | 68,616 | 57,801 | 53,369 | 40,155 | 31,906 | 11,791 | 12,561 | 7,877 | 5,917 |
| Douglas | 26,205 | 22,144 | 16,787 | 14,890 | 10,817 | 8,651 | 7,561 | 9,392 | 9,227 | 4,926 | 3,161 |
| Ferry | 6,295 | 5,811 | 3,655 | 3,889 | 4,096 | 4,701 | 4,292 | 5,143 | 4,800 | 4,562 | --- |
| Franklin | 37,473 | 35,025 | 25,816 | 23,342 | 13,563 | 6,307 | 6,137 | 5,877 | 5,153 | 486 | 696 |
| Garfield | 2,248 | 2,468 | 2,911 | 2,976 | 3,204 | 3,383 | 3,662 | 3,875 | 4,199 | 3,918 | 3,897 |
| Grant | 54,758 | 48,522 | 41,881 | 46,477 | 24,346 | 14,668 | 5,666 | 7,771 | 8,698 | --- | --- |
| Grays Harbor | 64,175 | 66,314 | 59,553 | 54,465 | 53,644 | 53,166 | 59,982 | 44,745 | 35,590 | 15,124 | 9,249 |
| Island | 60,195 | 44,048 | 27,011 | 19,638 | 11,079 | 6,098 | 5,369 | 5,489 | 4,704 | 1,870 | 1,787 |
| Jefferson | 20,146 | 15,965 | 10,661 | 9,639 | 11,618 | 8,918 | 8,346 | 6,557 | 8,337 | 5,712 | 8,368 |
| King | 1,507,319 | 1,269,749 | 1,156,633 | 935,014 | 732,992 | 504,980 | 463,517 | 389,273 | 284,638 | 110,053 | 63,989 |
| Kitsap | 189,731 | 147,152 | 101,732 | 84,176 | 75,724 | 44,387 | 30,776 | 33,162 | 17,647 | 6,767 | 4,624 |
| Kittitas | 26,725 | 24,877 | 25,039 | 20,467 | 22,235 | 20,230 | 18,154 | 17,737 | 18,561 | 9,704 | 8,777 |
| Klickitat | 16,616 | 15,822 | 12,138 | 13,455 | 12,049 | 11,357 | 9,825 | 9,268 | 10,180 | 6,407 | 5,167 |
| Lewis | 59,358 | 56,025 | 45,467 | 41,858 | 43,755 | 41,393 | 40,034 | 36,840 | 32,127 | 15,157 | 11,499 |
| Lincoln | 8,864 | 9,604 | 9,572 | 10,919 | 10,970 | 11,361 | 11,876 | 15,141 | 17,539 | 11,969 | 9,312 |
| Mason | 38,341 | 31,184 | 20,918 | 16,251 | 15,022 | 11,603 | 10,060 | 4,919 | 5,156 | 3,810 | 2,826 |
| Okanogan | 33,350 | 30,639 | 25,867 | 25,520 | 29,131 | 24,546 | 18,519 | 17,094 | 12,887 | 4,689 | 1,467 |
| Pacific | 18,882 | 17,237 | 15,796 | 14,674 | 16,558 | 15,928 | 14,970 | 14,891 | 12,532 | 5,983 | 4,358 |
| Pend Oreille | 8,915 | 8,580 | 6,025 | 6,914 | 7,413 | 7,156 | 7,155 | 6,363 | --- | --- | --- |
| Pierce | 586,203 | 485,643 | 411,027 | 321,590 | 275,876 | 182,081 | 163,842 | 144,127 | 120,812 | 55,515 | 50,940 |
| San Juan | 10,035 | 7,838 | 3,856 | 2,872 | 3,245 | 3,157 | 3,097 | 3,605 | 3,603 | 2,928 | 2,072 |
| Skagit | 79,555 | 64,138 | 52,381 | 51,350 | 43,273 | 37,650 | 35,142 | 33,373 | 29,241 | 14,272 | 8,747 |
| Skamania | 8,289 | 7,919 | 5,845 | 5,207 | 4,788 | 4,633 | 2,891 | 2,357 | 2,887 | 1,688 | 774 |
| Snohomish | 465,642 | 337,720 | 265,236 | 172,199 | 111,580 | 88,754 | 78,861 | 67,690 | 59,209 | 23,950 | 8,514 |
| Spokane | 361,364 | 341,835 | 287,487 | 278,333 | 221,561 | 164,652 | 150,477 | 141,289 | 139,404 | 57,542 | 37,487 |
| Stevens | 30,948 | 28,979 | 17,405 | 17,884 | 18,580 | 19,275 | 18,550 | 21,605 | 25,297 | 10,543 | 4,341 |
| Thurston | 161,238 | 124,264 | 76,894 | 55,049 | 44,884 | 37,285 | 31,351 | 22,366 | 17,581 | 9,927 | 9,675 |
| Wahkiakum | 3,327 | 3,832 | 3,592 | 3,426 | 3,835 | 4,286 | 3,862 | 3,472 | 3,285 | 2,819 | 2,526 |
| Walla Walla | 48,439 | 47,435 | 42,176 | 42,195 | 40,135 | 30,547 | 28,441 | 27,539 | 31,931 | 18,680 | 12,224 |
| Whatcom | 127,780 | 106,701 | 81,950 | 70,317 | 66,733 | 60,355 | 59,128 | 50,600 | 49,511 | 24,116 | 18,591 |
| Whitman | 38,775 | 40,103 | 37,900 | 31,263 | 32,469 | 27,221 | 28,014 | 31,323 | 33,280 | 25,360 | 19,109 |
| Yakima | 188,823 | 172,508 | 144,971 | 145,112 | 135,723 | 99,019 | 77,402 | 63,710 | 41,709 | 13,462 | 4,429 |
| County | 1880 | 1870 | 1860 | 1850 | Notes |
|---|---|---|---|---|---|
| WASHINGTON | 75,116 | 23,955 | 11,594 | 1,201 | See note 1 |
| Adams | --- | --- | --- | --- | *Whitman |
| Asotin | --- | --- | --- | --- | *Columbia |
| Benton | --- | --- | --- | --- | *Yakima, Klickitat |
| Chelan | --- | --- | --- | --- | *Okanogan, Kittitas |
| Clallam | 638 | 408 | 149 | --- | *Lewis |
| Clark | 5,490 | 3,081 | 2,384 | 643 | |
| Columbia | 7,103 | --- | --- | --- | *Walla Walla |
| Cowlitz | 2,062 | 730 | 406 | --- | *Lewis, Clark |
| Douglas | --- | --- | --- | --- | *Spokane |
| Ferry | --- | --- | --- | --- | *Stevens |
| Franklin | --- | --- | --- | --- | *Whitman |
| Garfield | --- | --- | --- | --- | *Columbia |
| Grant | --- | --- | --- | --- | *Douglas |
| Grays Harbor | 921 | 401 | 285 | --- | *Lewis; 1860-1910: Chehalis |
| Island | 1,087 | 626 | 294 | --- | *Lewis; Clark |
| Jefferson | 1,712 | 1,268 | 531 | --- | *Lewis |
| King | 6,910 | 2,120 | 302 | --- | *Lewis; Clark |
| Kitsap | 1,738 | 866 | 544 | --- | *Lewis |
| Kittitas | --- | --- | --- | --- | *Yakima |
| Klickitat | 4,055 | 329 | 230 | --- | *Clark |
| Lewis | 2,600 | 888 | 384 | 558 | |
| Lincoln | --- | --- | --- | --- | *Spokane |
| Mason | 639 | 289 | 162 | --- | *Lewis; 1860: Sawamish |
| Okanogan | --- | --- | --- | --- | *Stevens |
| Pacific | 1,645 | 738 | 420 | --- | *Lewis |
| Pend Oreille | --- | --- | --- | --- | *Stevens |
| Pierce | 3,319 | 1,409 | 1,115 | --- | *Lewis; Clark |
| San Juan | 948 | 554 | --- | --- | See note 2 |
| Skagit | --- | --- | --- | --- | *Whatcom |
| Skamania | 809 | 133 | 173 | --- | *Clark; Lewis |
| Snohomish | 1,387 | 599 | --- | --- | *Island |
| Spokane | 4,262 | --- | --- | --- | See notes 1 and 3 |
| Stevens | 1,245 | 734 | 996 | --- | See note 3 |
| Thurston | 3,270 | 2,246 | 1,507 | --- | *Lewis; Clark |
| Wahkiakum | 1,598 | 270 | 42 | --- | *Lewis |
| Walla Walla | 8,716 | 5,300 | 1,318 | --- | *Clark |
| Whatcom | 3,137 | 534 | 352 | --- | *Lewis; Clark |
| Whitman | 7,014 | --- | --- | --- | *Stevens |
| Yakima | 2,811 | 432 | --- | --- | *Walla Walla; Klickitat |
After a period when Great Britain also claimed it, Washington was definitively acquired in 1846 and was included in Oregon Territory, established in 1848. Washington became a separate territory in 1853, acquired essentially its present boundaries in 1863, and was admitted as a State on November 11, 1889.
The 1850 population is that of Clark and Lewis Counties, Oregon Territory; census coverage extended only to the southwestern part of present-day Washington. In 1860 census coverage included nearly the whole present State, and some persons in present-day northern Idaho and northwestern Montana.
County Notes:
Note 1: Areas shown for 1850 were then in Oregon Territory. Total for 1890 includes population (7,842) of certain Indian reservations not reported by county.
Note 2: The San Juan Islands were in dispute with Great Britain until 1872, and were reported in the 1870 census as "the disputed islands." San Juan County was formed in 1873.
Note 3: The first Spokane County was renamed Stevens in 1864. The present Spokane County was formed from Stevens after 1870.