{"nrhp_refnum":"82004614","name":"Gianella Bridge","other_names":["Sacramento River Bridge at Hamilton City"],"category":"structure","location":{"address":"CA 32","address_restricted":false,"city":"Hamilton City","county":"Glenn County","state":"CA","lat":39.751030928000034,"lon":-121.99726022799996,"geom_source":"nps_gis"},"listed_date":"1982-07-08","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation"],"significance_levels":["local"],"summary":{"what_it_is":"A steel through Pratt truss swing-span bridge carrying State Highway 32 across the Sacramento River at Hamilton City, between Glenn and Butte Counties, California. It was built 1908-1911 by Cotton Brothers & Co. to a design by John B. Leonard.","why_significant":"It is the oldest swing span movable bridge on the State highway system. Its construction marked a rare instance of cooperation between two rival counties. It is also the only known steel bridge by engineer John B. Leonard, and it supported the sugar beet industry around Hamilton City.","narrative":"Carrying State Highway 32 over the Sacramento River at Hamilton City, this steel bridge links Glenn and Butte Counties. It has two Pratt truss approach spans of 133 feet each and a 311-foot swing span, all resting on mass concrete piers. Built between 1908 and 1910 by Cotton Brothers of Oakland and opened in early 1911 after delays, it was designed by John B. Leonard, a leading state bridge engineer who usually worked in reinforced concrete. The counties chose steel because it cost less at first. The crossing location, favored by Butte County farmer Vincenzo Gianella, served the sugar beet refinery at Hamilton City, and the two rival counties cooperated to build it. It is the oldest swing span movable bridge on the State highway system. The deck was replaced in 1937 and again in 1954, and the swing span has stayed closed to river traffic since a 1972 agreement with the Coast Guard.","period_of_significance":"1908-1911","architect_builder":"Cotton Brothers & Co., Contractors / John B. Leonard, C.E.","architectural_style":null,"criteria":[],"status_note":"Altered but in good condition; the swing span has not been opened since 1972, though it must be restorable to opening within six months of Coast Guard notice.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:54:28.151708-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/82004614.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/82004614/4b5f5d29ab-800.webp","url_1600":"https://nationalhistoricalregister.com/media/82004614/4b5f5d29ab-1600.webp","licence":"Public domain","author":"Pete Asano, Photographer","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Gianella_Bridge,_Spanning_Sacramento_River_at_State_Highway_32,_Hamilton_City_vicinity_(Glenn_County,_California).jpg\" rel=\"noopener\">Pete Asano, Photographer</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Gianella_Bridge,_Spanning_Sacramento_River_at_State_Highway_32,_Hamilton_City_vicinity_(Glenn_County,_California).jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123858711","wikipedia":"https://en.wikipedia.org/wiki/Gianella_Bridge","wikidata":"https://www.wikidata.org/wiki/Q14682015"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/glenn-county/gianella-bridge-82004614/"}