The state of Washington is divided into 39 counties. Clark County is the oldest (founded in 1845), while Pend Oreille County is the youngest (established in 1911).

King County is the most populous, with a population of 1,931,249 people. Okanogan County has the most land area (13,644 km2), while San Juan County has the smallest (453 km2).

Please find a list of all Washington counties listed alphabetically below.

• Adams County, WA
• Asotin County, WA
• Benton County, WA
• Chelan County, WA
• Clallam County, WA
• Clark County, WA
• Columbia County, WA
• Cowlitz County, WA
• Douglas County, WA
• Ferry County, WA
• Franklin County, WA
• Garfield County, WA
• Grant County, WA
• Grays Harbor County, WA
• Island County, WA
• Jefferson County, WA
• King County, WA
• Kitsap County, WA
• Kittitas County, WA
• Klickitat County, WA
• Lewis County, WA
• Lincoln County, WA
• Mason County, WA
• Okanogan County, WA
• Pacific County, WA
• Pend Orielle County, WA
• Pierce County, WA
• San Juan County, WA
• Skagit County, WA
• Skamania County, WA
• Snohomish County, WA
• Spokane County, WA
• Stevens County, WA
• Thurston County, WA
• Wahkiakum County, WA
• Walla Walla County, WA
• Whatcom County, WA
• Whitman County, WA
• Yakima County, WA