{"nrhp_refnum":"86000015","name":"Armstrong Tunnel","other_names":[],"category":"structure","location":{"address":"Between Forbes and Second Aves. at S. Tenth St.","address_restricted":false,"city":"Pittsburgh","county":"Allegheny County","state":"PA","lat":40.43798509700008,"lon":-79.99216885599998,"geom_source":"nps_gis"},"listed_date":"1986-01-07","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation"],"significance_levels":["local"],"summary":{"what_it_is":"A 1,300-foot reinforced concrete and steel girder automobile tunnel with rock-faced sandstone portals, running through the Bluff on the north side of the Monongahela River just east of downtown Pittsburgh, Allegheny County, Pennsylvania. It was built in 1926-27.","why_significant":"The nomination argues the tunnel reflects the early-twentieth-century automobile tunnel building boom, the topographic and political conditions particular to Pittsburgh, and local engineering skill. It was part of a county public works program of the 1920s and 1930s and is regarded as Allegheny County's best-preserved example of a major historic tunnel and a local engineering landmark.","narrative":"Built between January 1926 and May 1927 through the Bluff, a riverside bluff on the north side of the Monongahela River east of downtown Pittsburgh, this 1,300-foot twin-tube automobile tunnel was designed by the Allegheny County Bureau of Bridges under engineer Vernon R. Covell, with portals by county architect Stanley Roush and construction by Booth & Flinn Company. Its reinforced concrete barrel-vault tubes and steel girders carry traffic between a north portal at Forbes Avenue and a south portal at Second Avenue, where a dogleg route was needed to meet a perpendicular intersection. The rock-faced sandstone portals, with dressed granite trim and a cornice inscribed with the tunnel's name, show a spare Moderne treatment of Classical forms. It was named for County Commissioner Joseph G. Armstrong, a leading advocate of the project. It is regarded as the county's best-preserved major historic tunnel and a local engineering landmark, reflecting 1920s public works and the difficulty of crossing the Bluff by road.","period_of_significance":"1926-27","architect_builder":"Vernon R. Covell; Stanley L. Roush; Booth & Flinn Company (contractor)","architectural_style":"Classically derived detailing interpreted in a spare Moderne mode","criteria":[],"status_note":"Described as in good condition and unaltered, though the surroundings have changed with a street above the north portal and an elevated exit ramp partly obscuring the south portal.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:33.597991-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/86000015.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/86000015/766f834b42-800.webp","url_1600":"https://nationalhistoricalregister.com/media/86000015/766f834b42-1600.webp","licence":"CC BY 3.0","author":"Alekjds","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:ArmstrongTunnel.JPG\" rel=\"noopener\">Alekjds</a>, <a href=\"https://creativecommons.org/licenses/by/3.0\" rel=\"license noopener\">CC BY 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:ArmstrongTunnel.JPG"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71997808","wikipedia":"https://en.wikipedia.org/wiki/Armstrong_Tunnel","wikidata":"https://www.wikidata.org/wiki/Q4794005"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/allegheny-county/armstrong-tunnel-86000015/"}