{"nrhp_refnum":"00000525","name":"San Francisco-Oakland Bay Bridge (Additional Documentation)","other_names":["Bay Bridge"],"category":"structure","location":{"address":"I-80","address_restricted":false,"city":"San Francisco","county":"San Francisco","state":"CA","lat":37.80437204800006,"lon":-122.36134626079036,"geom_source":"nps_gis"},"listed_date":"2001-08-13","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Architecture","Engineering"],"significance_levels":["national"],"summary":{"what_it_is":"A combined suspension, cantilever-truss and tunnel bridge system carrying I-80 across San Francisco Bay between San Francisco and Oakland via Yerba Buena Island, completed in 1936. It includes approach viaducts, a transit terminal building and electrical substations.","why_significant":"The nomination argues the bridge is significant for engineering and transportation. It was the longest bridge in the world when built and combined several bridge types in one structure. Its double-suspension West Bay crossing was considered the first of its kind, and its design answered poor foundation conditions on the bay floor. It also carried automobile, truck and interurban rail traffic and provided Depression-era jobs.","narrative":"Spanning San Francisco Bay between San Francisco and Oakland, the Bay Bridge opened in 1936 as the longest bridge in the world. It links five segments: the San Francisco approach, a West Bay crossing of two back-to-back suspension spans, a tunnel and viaducts through Yerba Buena Island, an East Bay crossing, and the Oakland approach. Built of steel and reinforced concrete, it originally carried automobiles on the upper deck and trucks plus interurban trains on the lower deck. Changes in the late 1950s removed the rail tracks and converted both decks to one-way car and truck traffic. The bridge is recognized for engineering and transportation. Its double-suspension design was considered the first of its kind, and its deep piers and varied bridge types responded to poor seabed conditions. Construction also provided work during the Great Depression. Associated resources include a granite-faced transit terminal and Key System electrical substations.","period_of_significance":"1936","architect_builder":"Purcell, Charles H.; Andrew, Charles E.; Woodruff, Glenn B.","architectural_style":"Other: Combination cantilever-truss/suspension-truss spans and tunnel","criteria":["A","C"],"status_note":"Still carries road traffic. Rail service was removed in the late 1950s and the decks were converted to one-way mixed car and truck traffic. Original Oakland approaches no longer remain.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:54:27.739386-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/00000525.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/00000525/c0b99b06e0-800.webp","url_1600":"https://nationalhistoricalregister.com/media/00000525/c0b99b06e0-1600.webp","licence":"CC BY-SA 3.0","author":"ChristianSchd","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Oakland_Bay_Bridge_Western_Part.jpg\" rel=\"noopener\">ChristianSchd</a>, <a href=\"https://creativecommons.org/licenses/by-sa/3.0\" rel=\"license noopener\">CC BY-SA 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Oakland_Bay_Bridge_Western_Part.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123861295","wikipedia":"https://en.wikipedia.org/wiki/San_Francisco%E2%80%93Oakland_Bay_Bridge","wikidata":"https://www.wikidata.org/wiki/Q771404"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/san-francisco/san-francisco-oakland-bay-bridge-additional-documentation-00000525/"}