{"nrhp_refnum":"74001745","name":"Smithfield Street Bridge","other_names":[],"category":"structure","location":{"address":"Smithfield St. at the Monongahela River","address_restricted":false,"city":"Pittsburgh","county":"Allegheny County","state":"PA","lat":40.43485028050003,"lon":-80.0021489324649,"geom_source":"nps_gis"},"listed_date":"1974-03-21","is_nhl":true,"nhl_designated_date":"1976-05-11","areas_of_significance":["Engineering"],"significance_levels":["national"],"summary":{"what_it_is":"A steel lenticular truss bridge carrying Smithfield Street across the Monongahela River in Pittsburgh, Allegheny County, Pennsylvania. It was built in 1883 with a second lane added in 1889 and the truss widened in 1911.","why_significant":"The nomination argues the bridge is an early and creative use of steel in bridge design and a graceful example of the double lenticular truss. Its Romanesque-style entrance arches, built of steel and iron, are presented as a notable expression of late Victorian engineering. It is described as an early statement of American industrial growth and as incorporating the largest lenticular trusses in the country.","narrative":"Smithfield Street crosses the Monongahela River in Pittsburgh on a double lenticular, or Pauli, truss bridge completed in 1883. Designed by Gustave Lindenthal, one of the best-known bridge engineers of his time, it replaced an earlier suspension bridge designed by John A. Roebling, which had itself succeeded a span from 1818 that burned in 1845. The original single lane was twenty feet wide, and a second lane of the same width was added on the upstream side in 1889, with the truss widened in 1911. Six curved steel trusses rest on rusticated stone piers. The entrance arches were built in a Norman Romanesque style, with basket-handle arches, corbeled imposts, and a crenelated cornice, and they use steel and iron rather than masonry. The bridge is regarded as an early example of steel's use in bridge engineering and as one of the most important lenticular truss spans in the country.","period_of_significance":"1883-1889","architect_builder":"Gustave Lindenthal (designer)","architectural_style":"Norman Romanesque entrance arches; lenticular truss","criteria":["C"],"status_note":"The bridge remains in very good condition according to the description, though the condition checkbox marked fair.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:30.772799-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/74001745.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/74001745/b2ef97010b-800.webp","url_1600":"https://nationalhistoricalregister.com/media/74001745/b2ef97010b-1600.webp","licence":"CC BY 2.0","author":"David Wilson from Oak Park, Illinois, USA","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:19660415_12_PAT_1620_on_Smithfield_St._bridge.jpg\" rel=\"noopener\">David Wilson from Oak Park, Illinois, USA</a>, <a href=\"https://creativecommons.org/licenses/by/2.0\" rel=\"license noopener\">CC BY 2.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:19660415_12_PAT_1620_on_Smithfield_St._bridge.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71997800","wikipedia":"https://en.wikipedia.org/wiki/Smithfield_Street_Bridge","wikidata":"https://www.wikidata.org/wiki/Q7545513"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/allegheny-county/smithfield-street-bridge-74001745/"}