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King County, through its public works agencies, has been historically responsible for the siting, construction, inspection, maintenance, repair and replacement of highway bridges, overcrossings, and undercrossings within its jurisdiction. The county maintains a record of these activities for each bridge.

Please contact the King County Archives for information about the following records. The records are most easily accessed by bridge number(s), bridge names, section-township-range coordinates, or other subject term. Archives staff can help you determine the best access point for your search.

Bridge files, 1901-1994

These files constitute a textual record of highway bridges built by, transferred to, or eliminated by King County between 1901 and 1994. During this period, bridge engineering was undertaken by the County Surveyor (1901-1907), County Engineer (1907-1937, 1949-1969), Road Engineer (1937-1938), the Engineering Department (1938-1969) and the Department of Public Works (1970-1994).

The files document these agencies' construction, inspection, maintenance, repair and replacement of bridges and of railroad and highway overcrossings and undercrossings.

Record types include construction documents (e.g., cost estimates, contractor estimates, engineering notes and calculations, contract documents); inspection reports; correspondence; structure plans; site maps; and shop drawings; photographs; and newspaper or journal articles.

Bridge files: photographs, 1904-1988

This series is composed of bridge photographs, mostly dating from three general time periods: 1910-1920, 1932-1936, and 1950-1988. Bridges were assigned one or more identifying numbers by the county. The agency record for each bridge includes bridge number; bridge name if applicable; location (name of street or road, nearest city or town, section-township-range coordinates); and name of watercourse, railroad or highway spanned by the structure. Added information includes type of photographic materials present, date span of photographs, and limited keywords describing image content. The photograph files are arranged numerically by the bridge number best representing the bulk of the photographs in a given folder. Within each folder, photographs are arranged in approximate chronological order. Negatives are present for many bridge images (particularly for the period 1910-1936) and are filed separately by bridge number.

Bridge files: maps and plans, 1901-1994

This series is composed of oversized site and vicinity maps; structural plans; standard detail drawings; and field and survey sketches. In general, graphic materials measuring 8.5 by 14 inches or less have been retained in the Bridge Files series. The oversized graphic materials in this series are present in various physical formats, primarily reproductions using various processes (blueprint, blueline, brownline, xerographic). Field sketches may be original pencil or ink drawings on paper. Accessions from the online Map Vault of the King County Road Services Division may contain original versions of reproduced drawings found in this series.

TTY Relay 711

Monday, Tuesday, Thursday, and Friday: 9 am-4 pm

Please note the Archives is closed Wednesdays.