{"nrhp_refnum":"82002233","name":"I Street Bridge","other_names":[],"category":"structure","location":{"address":"CA 16","address_restricted":false,"city":"Sacramento","county":"Sacramento County","state":"CA","lat":38.57735629100006,"lon":-121.50615538199997,"geom_source":"nps_gis"},"listed_date":"1982-04-22","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation"],"significance_levels":["local"],"summary":{"what_it_is":"A double-deck steel truss bridge carrying State Highway 16 over the Sacramento River between Sacramento and Yolo Counties, California, built in 1911 by Southern Pacific with steel from the American Bridge Company.","why_significant":"The nomination argues the bridge is a substantial reminder of the Southern Pacific improvements made under E.H. Harriman. Its center-bearing swing span was the heaviest in the world when built and remains the heaviest in the U.S. It represents a bridge type, an early twentieth century period, and shop-fabricated, field-riveted steel truss construction.","narrative":"Spanning the Sacramento River between Sacramento and Yolo Counties, this double-deck steel truss bridge carries State Highway 16 on its concrete upper deck and the Southern Pacific's double-track main line below. Completed in 1911, it replaced a single-track timber Howe truss swing bridge in use since the 1860s that had become a bottleneck on the railroad's main line. Construction began in June 1910 under an agreement between the railroad and the two counties. The bridge has 33 spans totaling 2,194 feet. Its center-bearing swing span weighs about 6,300,000 pounds and was the heaviest in the world when built; it is still the heaviest in the United States. American Bridge Company supplied the roughly 4,500 tons of steel, and John D. Isaacs directed the design. New approaches built in 1937 and 1959 slightly affected its design integrity, but the bridge remains a substantial reminder of the Harriman-era improvements to the Southern Pacific.","period_of_significance":"1900-","architect_builder":"Southern Pacific/American Bridge Co.; designed under Southern Pacific consulting engineer John D. Isaacs","architectural_style":null,"criteria":[],"status_note":"Listed as occupied, in excellent condition and altered; it still carries Southern Pacific main line tracks on the lower deck and State Highway 16 on the upper deck. Approaches were rebuilt in 1937 and 1959.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:31.395463-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_CA/82002233.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/82002233/4fcd2f139f-800.webp","url_1600":"https://nationalhistoricalregister.com/media/82002233/4fcd2f139f-1600.webp","licence":"CC BY-SA 3.0","author":"Xde13","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:I_Street_Bridge_(Sacramento).jpg\" rel=\"noopener\">Xde13</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:I_Street_Bridge_(Sacramento).jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/123860608","wikipedia":"https://en.wikipedia.org/wiki/I_Street_Bridge","wikidata":"https://www.wikidata.org/wiki/Q5979075"},"indexable":true,"url":"https://nationalhistoricalregister.com/california/sacramento-county/i-street-bridge-82002233/"}