Counties Washington State Freight Truck Origin and Destination Study (by County) Adams County Lewis County Asotin County Lincoln County Benton County Mason County Chelan County Okanogan County Clallam County Pacific County Clark County Pend Oreille County Columbia County Pierce County Cowlitz County San Juan County Douglas County Skagit County Ferry County Skamania County Franklin County Snohomish County Garfield County Spokane County Grant County Stevens County Grays Harbor County Thurston County Island County Wahkiakum County Jefferson County Walla Walla County King County Whatcom County Kitsap County Whitman County Kittitas County Yakima County Klickitat County