{"nrhp_refnum":"04000774","name":"First Street Bridge","other_names":["Bridge No. 21C-95"],"category":"structure","location":{"address":"First St. across the Napa R","address_restricted":false,"city":"Napa","county":"Napa County","state":"CA","lat":38.301577363000035,"lon":-122.27933749999994,"geom_source":"nps_gis"},"listed_date":"2004-08-05","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering"],"significance_levels":["local"],"summary":{"what_it_is":"A three-span reinforced concrete T-girder bridge, about 155 feet long and 61 feet wide, carrying First Street across the Napa River in Napa, California. It was built in 1914, designed by Leonard and Day and built by C. H. Gildersleeve.","why_significant":"The bridge is significant under Criterion C in the area of Engineering as an excellent example of early twentieth-century reinforced concrete girder bridge construction in California. It was built when concrete girder bridges were still cutting-edge technology. It is also valued for its sweeping central arch and for being the work of Leonard and Day, whose senior partner John B. Leonard was among the state's most important concrete bridge designers.","narrative":"Carrying First Street over the Napa River about half a mile from downtown Napa, this reinforced concrete bridge was completed in 1914. It measures roughly 155 feet long and 61 feet wide, with three spans supported by four T-girders. In elevation it shows a central arch flanked by two half-arches, along with pilasters, buttresses, scored quoin-like end walls and a parapet with recessed panels. Pylons at the ends mark the railings, and a plaque names the mayor, council members, engineers and contractor. Leonard and Day designed the bridge and C. H. Gildersleeve built it. It was listed for its engineering importance: concrete girder bridges only began appearing in California around 1910, and a 1986 state survey rated this one among the best of hundreds, with only six judged more important. Its early date, technical merit, appealing arch and designers all contributed. Apart from asphalt on the deck, it appears unaltered and remains a working road crossing.","period_of_significance":"1914","architect_builder":"Leonard and Day (designer); Gildersleeve, C. H. (contractor)","architectural_style":"Other: Concrete Girder Bridge","criteria":["C"],"status_note":"Still in vehicular use; the structure appears unaltered apart from a layer of asphalt on the deck.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:54:29.506712-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/04000774.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/04000774/d538198b87-800.webp","url_1600":"https://nationalhistoricalregister.com/media/04000774/d538198b87-1600.webp","licence":"Public domain","author":"David DeVries, Photographer","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:First_Street_Bridge,_Spanning_Napa_River_at_First_Street_between_Soscol,_Napa_(Napa_County,_California).jpg\" rel=\"noopener\">David DeVries, Photographer</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:First_Street_Bridge,_Spanning_Napa_River_at_First_Street_between_Soscol,_Napa_(Napa_County,_California).jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123857686","wikipedia":"https://en.wikipedia.org/wiki/First_Street_Bridge_(Napa,_California)","wikidata":"https://www.wikidata.org/wiki/Q78497242"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/napa-county/first-street-bridge-04000774/"}