Plat Records

Official copies of plat maps are filed with the King County Recorder's Office.

The Map Vault Collection of the King County Road Services Division can often provide researchers with electronic versions of many plat maps and recorded binding site plans. Paper versions of many plat maps can also be viewed onsite at the King County Archives.

Plats are accepted, established and modified by the King County Council (prior to 1969, the King County Commissioners). To find the actual Council ordinance or Commissioner resolution establishing or modifying a specific plat, see the county's Legislative Files or contact the King County Archives.

Additional information about the establishment or modification of plats, pre-1969, can be found in the Commissioners' plat application files (1916-1970). These applications were submitted for the final approval of a plat by the Commissioners. Individual files typically contain a certificate prepared by an attorney indicating that the ownership of the property and the payment of taxes have been verified, along with the recommendations from the office of the County Engineer. A small number of the files contain plat maps. The files are arranged by an office filing number. Contact the King County Archives for additional information and assistance.

Plats, and platted road and street rights-of-way, are vacated by the King County Council. To find the actual Council ordinance see the county's Legislative Files or contact the King County Archives.

Plat vacations prior to 1969 were sometimes made by resolutions of the King County Commissioners. More often they were made by direct orders of the Commissioners. Texts of plat vacation orders can be found in the Commissioners' Proceedings or in their plat vacation files. These files are arranged by vacation order number (5024 to 8464). They also include supporting documentation such as petitions, maps, engineers' reports and correspondence. For assistance in locating a plat vacation order, please contact the King County Archives. It is helpful if you have a date, or an approximate date, of the plat vacation.

Short plats are a simplified way of subdividing property. The main condition placed on short plats is that no more than four (4) new properties can be made out of any one (1) parcel.

Short plattings after September 1972 are filed with the King County Recorder's Office. (Washington State did not require the recording of short plats until 1974, via RCW 58.17). For questions and assistance, call the Recorder's Office Customer Research specialist in plats and surveys at (206) 296-1842.

For properties short-platted before September 1972, this information is usually present on the King County Assessors' Property Record Cards, which are held by the Puget Sound [state] Regional Archives (external link) in Bellevue. The notation on the cards might refer to a "KC SUBD Application." This refers to a subdividing available before King County adopted its short subdivision code in 1972. If a proposed segregation resulted in the creation of four or less lots out of the parent parcel, the application was typically approved. Even if not shown on the King County Assessor's maps, these unrecorded approved lots are still recognized, if the lots can be established in the configuration shown on the application.

Sometimes old documents and maps will refer to an "unrecorded plat." Prior to 1948, some King County plats were unrecorded. Commissioners' Resolution 11048 (March 23, 1948) changed all existing unrecorded plats to "preliminary plats." Preliminary plats were generally finalized after an accurate survey was undertaken and approved. For assistance in associating a former "unrecorded plat" with a past or current tax parcel, please contact the King County Department of Assessments.