Washington County Codes

In 1935, Washington began to issue license plates by county. A one- or two-letter prefix denoted the county, and letters were assigned by the order of population, with King County, the most populous, receiving letter A, followed by Pierce with B, and so on. After letter Z, the 13 smallest counties received two-letter prefixes derived from the county name.

1935 County Plates cropped
This photo from the Washington State Archives shows a complete county set from the first year of county coding, taken on the steps of the northeast corner of the state capitol

In 1954 the system remained the same, except the county code became a suffix. In 1958, the codes were adapted to conform with the ABC 123 numbering format. By 1980 the system became too complex to manage and the state discontinued the practice.

County Seat 1935-1957 1958-1981
King Seattle A AAA-AZZ, OAA-OZZ, IAA-IZZ, UCA-UKZ
Pierce Tacoma B BAA-BZZ, TBA-TFZ
Spokane Spokane C CAA-CZZ, SLA-SMZ (excl CLx, CMx, CUx)
Snohomish Everett D DAA-DVR (excl DSA-DUZ)
Yakima Yakima E EAA-EKZ
Whatcom Bellingham F FAA-FFP
Clark Vancouver G GAA-GND, HHA-HHZ
Grays Harbor Montesano H HAA-HDP
Kitsap Port Orchard I KSA-KYZ
Thurston Olympia J JAA-JEE
Chelan Wenatchee K KAA-KDC
Lewis Chehalis L LAA-LDG
Skagit Mount Vernon M MAA-MDS
Cowlitz Kelso N NAA-NFR
Walla Walla Walla Walla O WWA-WYP
Whitman Colfax P PAA-PCF
Clallam Port Angeles Q CLA-CMZ, PDA-PDF
Benton Prosser R RAA-REU
Kittitas Ellensburg S SAA-SBH
Lincoln Davenport T TAA-TAN
Okanogan Okanogan U UAA-UBJ
Pacific South Bend V VAA-VAW
Stevens Colville W WAA-WBC
Mason Shelton X XAA-XAZ
Jefferson Port Townsend Y YAA-YAM
Klickitat Goldendale Z ZAA-ZBD
Adams Ritzville AD YYA-YYR
Asotin Asotin AN ZYA-ZYL, ZZA-ZZZ
Columbia Dayton CO CUA-CUG
Douglas Waterville DO DSA-DST
Franklin Pasco FN FNA-FSF
Ferry Republic FY FYA-FYE
Garfield Pomeroy GA GDA-GDF
Grant Ephrata GT GTA-GVW
Island Coupeville IS 1958: CVA-CVL   1963 up: ISA-ITH
Pend Oreille Newport PO PEB-PES
San Juan Friday Harbor SJ SJA-SJG
Skamania Stevenson SA SKA-SKJ
Wahkiakum Cathlamet WA WMA-WMF
Dept. of Licensing JJ JJA-JJZ, XXA-XXZ
Dept. of Licensing (1939-1942) LD