| County | FIPS-code | Provincie zetel | Gevestigd | Oorsprong | Betekenis van de naam | Bevolking | Gebied | Kaart |
| Adams County | 001 | Ritzville | 1883 | Whitman County | John Adams (1735-1826), 2e president van de V.S. | 7004187280000000000♠18,728 | 7003192500000000000♠1,925 sq mi
(7003498600000000000♠4,986 km2) | 
|
| Asotin County | 003 | Asotin | 1883 | Garfield County | De Nez Percé naam voor Eel Creek | 7004216230000000000♠21,623 | 7002636000000000000♠636 sq mi
(7003164700000000000♠1,647 km2) | 
|
| Benton County | 005 | Prosser | 1905 | Yakima en Klickitat Counties | Thomas Hart Benton (1782-1858), senator in Missouri. | 7005175177000000000♠175,177 | 7003170300000000000♠1,703 sq mi
(7003441100000000000♠4,411 km2) | 
|
| Chelan County | 007 | Wenatchee | 1899 | Okanogan en Kittitas Counties | Een indiaans woord dat "diep water" betekent, waarschijnlijk verwijzend naar Lake Chelan | 7004724530000000000♠72,453 | 7003292200000000000♠2,922 sq mi
(7003756800000000000♠7,568 km2) | 
|
| Clallam County | 009 | Port Angeles | 1854 | Jefferson County | Een Klallam woord dat "het sterke volk" betekent | 7004714040000000000♠71,404 | 7003174500000000000♠1,745 sq mi
(700345200000000♠4,520 km2) | 
|
| Clark County | 011 | Vancouver | 1845 | Oorspronkelijk graafschap | William Clark (1770-1838), de co-kapitein van de Lewis en Clark Expeditie | 7005425363000000000♠425,363 | 700262800000000♠628 sq mi
(7003162700000000000♠1,627 km2) | 
|
| Columbia County | 013 | Dayton | 1875 | Walla Walla County | De Columbia Rivier | 7003407800000000000♠4,078 | 700286900000000♠869 sq mi
(7003225100000000000♠2,251 km2) | 
|
| Cowlitz County | 015 | Kelso | 1854 | Oorspronkelijk graafschap | Cowlitz, een Indiaanse stam | 7005102410000000000♠102,410 | 7003113900000000000♠1,139 sq mi
(7003295000000000000♠2,950 km2) | 
|
| Douglas County | 017 | Waterville | 1883 | Lincoln County | Stephen A. Douglas (1813-1861), U.S. senator uit Illinois | 7004384310000000000♠38,431 | 7003182100000000000♠1,821 sq mi
(7003471600000000000♠4,716 km2) | 
|
| Ferry County | 019 | Republiek | 1899 | Stevens County | Elisha P. Ferry (1825-1895), 1e gouverneur van de staat Washington | 7003755100000000000♠7,551 | 7003220400000000000♠2,204 sq mi
(7003570800000000000♠5,708 km2) | 
|
| Franklin County | 021 | Pasco | 1883 | Whitman County | Benjamin Franklin (1706-1790), schrijver, redenaar, uitvinder en stichter van de V.S. | 7004781630000000000♠78,163 | 7003124200000000000♠1,242 sq mi
(7003321700000000000♠3,217 km2) | 
|
| Garfield County | 023 | Pomeroy | 1881 | Columbia County | James A. Garfield (1831-1881), 20e president van de V.S. | 7003226600000000000♠2,266 | 7002710000000000000♠710 sq mi
(7003183900000000000♠1,839 km2) | 
|
| Grant County | 025 | Ephrata | 1909 | Douglas County | Ulysses S. Grant (1822-1885), 18e president van de V.S. | 7004891200000000000♠89,120 | 7003268100000000000♠2,681 sq mi
(7003694400000000000♠6,944 km2) | 
|
| Grays Harbor County | 027 | Montesano | 1854 | Thurston County | Grays Harbor, een waterlichaam genoemd naar ontdekkingsreiziger en koopman Robert Gray (1755-1806) | 7004727970000000000♠72,797 | 7003191700000000000♠1,917 sq mi
(7003496500000000000♠4,965 km2) | 
|
| Island County | 029 | Coupeville | 1853 | Thurston County | Whidbey en Camano Eilanden | 7004785060000000000♠78,506 | 700220900000000♠209 sq mi
(700254100000000♠541 km2) | 
|
| JeffersonCounty | 031 | Port Townsend | 1852 | Thurston County | Thomas Jefferson (1743-1826), 3e president van de V.S. en belangrijkste auteur van de Onafhankelijkheidsverklaring | 7004298720000000000♠29,872 | 7003180900000000000♠1,809 sq mi
(7003468500000000000♠4,685 km2) | 
|
| King County | 033 | Seattle | 1852 | Thurston County | William R. King (1786-1853), vicepresident van de V.S. onder Franklin Pierce; in 1986 officieel hernoemd naar Martin Luther King, Jr. (1929–1968) | 7006193124900000000♠1,931,249 | 7003212600000000000♠2,126 sq mi
(7003550600000000000♠5,506 km2) | 
|
| Kitsap County | 035 | Port Orchard | 1857 | King en Jefferson Counties | Opperhoofd Kitsap (ged. 1860), leider van de Suquamish stam | 7005251133000000000♠251,133 | 7002396000000000000♠396 vierkante mijl
(7003102600000000000♠1,026 km2) | 
|
| KittitasCounty | 037 | Ellensburg | 1883 | Yakima County | Woord van de Kittitas-stam van onzekere betekenis, met populaire vertalingen variërend van "wit krijt" tot "land van overvloed". | 7004409150000000000♠40,915 | 7003229700000000000♠2,297 sq mi
(7003594900000000000♠5,949 km2) | 
|
| Klickitat County | 039 | Goldendale | 1859 | Walla Walla County | Klickitat stam | 7004203180000000000♠20,318 | 7003187200000000000♠1,872 sq mi
(7003484800000000000♠4,848 km2) | 
|
| LewisCounty | 041 | Chehalis | 1845 | Oorspronkelijk graafschap | Meriwether Lewis (1774-1809), de co-kapitein van de Lewis en Clark Expeditie | 7004754550000000000♠75,455 | 7003240800000000000♠2,408 sq mi
(7003623700000000000♠6,237 km2) | 
|
| Lincoln County | 043 | Davenport | 1883 | Whitman County | Abraham Lincoln (1809-1865), 16e president van de V.S. | 7004105700000000000♠10,570 | 7003231100000000000♠2,311 sq mi
(7003598500000000000♠5,985 km2) | 
|
| Mason County | 045 | Shelton | 1854 | King County | Charles H. Mason (1830-1859), eerste secretaris van het Washington Territory | 7004606990000000000♠60,699 | 70029610000000000♠961 sq mi
(7003248900000000000♠2,489 km2) | 
|
| Okanogan County | 047 | Okanogan | 1888 | Stevens County | Een Salish indiaans woord dat "rendez-vous" betekent. | 7004411200000000000♠41,120 | 7003526800000000000♠5,268 sq mi
(70041364400000000♠13,644 km2) | 
|
| Pacific County | 049 | South Bend | 1851 | Lewis County | De Stille Oceaan | 7004209200000000000♠20,920 | 700297500000000♠975 sq mi
(7003252500000000000♠2,525 km2) | 
|
| Pend OreilleCounty | 051 | Newport | 1911 | Stevens County | De Pend d'Oreille Indiaanse stam | 7004130010000000000♠13,001 | 7003140000000000000♠1,400 sq mi
(7003362600000000000♠3,626 km2) | 
|
| Pierce County | 053 | Tacoma | 1852 | Thurston County | Franklin Pierce (1804-1869), 14e president van de V.S. | 7005795225000000000♠795,225 | 7003167600000000000♠1,676 sq mi
(7003434100000000000♠4,341 km2) | 
|
| SanJuan County | 055 | Friday Harbor | 1873 | Whatcom County | San Juan Eiland | 7004157690000000000♠15,769 | 700217500000000♠175 vierkante mijl
(7002453000000000000♠453 km2) | 
|
| Skagit County | 057 | Mount Vernon | 1883 | Whatcom County | De Skagit Indiaanse stam | 7005116901000000000♠116,901 | 7003173500000000000♠1,735 sq mi
(7003449400000000000♠4,494 km2) | 
|
| Skamania County | 059 | Stevenson | 1854 | Clark County | Een Chinookan woord dat "snel water" betekent | 7004110660000000000♠11,066 | 7003165600000000000♠1,656 sq mi
(7003428900000000000♠4,289 km2) | 
|
| Snohomish County | 061 | Everett | 1861 | Island County | De Snohomish stam | 7005713335000000000♠713,335 | 700320900000000♠2,090 sq mi
(7003541300000000000♠5,413 km2) | 
|
| Spokane County | 063 | Spokane | 1879 | Stevens County | De Spokane Indiaanse stam | 7005471221000000000♠471,221 | 7003176400000000000♠1,764 sq mi
(7003456900000000000♠4,569 km2) | 
|
| Stevens County | 065 | Colville | 1863 | Walla Walla County | Isaac Stevens (1818-1862), 1e gouverneur van het Washington Territory | 7004435310000000000♠43,531 | 7003247800000000000♠2,478 sq mi
(7003641800000000000♠6,418 km2) | 
|
| Thurston County | 067 | Olympia | 1852 | Lewis County | Samuel Thurston (1815-1851), de eerste afgevaardigde van het Oregon Territory in het Congres van de V.S. | 7005252264000000000♠252,264 | 700272700000000♠727 sq mi
(7003188300000000000♠1,883 km2) | 
|
| Wahkiakum County | 069 | Cathlamet | 1854 | Cowlitz County | Leider van de Wahkiakum ("Tall Timber"), inheemse Amerikaanse stam | 7003397800000000000♠3,978 | 700226400000000♠264 sq mi
(7002684000000000000♠684 km2) | 
|
| Walla Walla County | 071 | Walla Walla | 1854 | Skamania County | De Walla Walla indianenstam, en ook een andere naam voor stromend water | 7004587810000000000♠58,781 | 700312700000000♠1,270 sq mi
(7003328900000000000♠3,289 km2) | 
|
| Whatcom County | 073 | Bellingham | 1854 | Island County | Nooksack woord dat "luidruchtig water" betekent | 7005201140000000000♠201,140 | 7003212000000000000♠2,120 sq mi
(7003549100000000000♠5,491 km2) | 
|
| Whitman County | 075 | Colfax | 1871 | Stevens County | Marcus Whitman (1802-1847), een presbyteriaanse missionaris | 7004447760000000000♠44,776 | 7003215900000000000♠2,159 sq mi
(7003559200000000000♠5,592 km2) | 
|
| Yakima County | 077 | Yakima | 1865 | Ferguson County (ter ziele) | De Yakama inheemse Amerikaanse stam | 7005243231000000000♠243,231 | 7003429600000000000♠4,296 sq mi
(70041112700000000♠11,127 km2) | 
|
