{"nrhp_refnum":"88000777","name":"McClay's Twin Bridge (East)","other_names":["McClay's Twin Bridge (West)"],"category":"structure","location":{"address":"LR 28010 over trib. to Conodoguinet Creek","address_restricted":false,"city":"Middle Spring","county":"Franklin County","state":"PA","lat":40.09851744200006,"lon":-77.57067749099997,"geom_source":"nps_gis"},"listed_date":"1988-06-22","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering"],"significance_levels":["state"],"summary":{"what_it_is":"A small multiple-span stone camelback turnpike bridge carrying the road over Conodoquinet Creek (a tributary) in Middle Spring, Franklin County, Pennsylvania, one of two such bridges built side by side on the same road.","why_significant":"The nomination describes it as a very fine example of a small, multiple-span nineteenth-century turnpike bridge built by Silas Harry, a master mason known for stone bridges along the National Road in Pennsylvania and Maryland. Few stone bridges of its kind in Franklin County survive, and its roughly coursed local limestone, semi-pyramidal piers and thin limestone coping are typical of county bridges built before 1860.","narrative":"Built in the late 1820s by the master mason Silas Harry, this small stone turnpike bridge carries the road across Conodoquinet Creek near Middle Spring in Franklin County, Pennsylvania. It has two arches of twenty-foot spans and extends 105 feet in total, with a stone parapet topped by a concrete cap. It is one of two camelback bridges Harry built side by side on the same road. Harry was known for stone bridges along the National Road in Pennsylvania and Maryland. Few stone bridges of this kind remain in Franklin County, and the county's bridge historian F. F. Unger documented them. The bridge is valued for its roughly coursed local limestone, its semi-pyramidal piers and its thin limestone coping, features typical of county bridges built before 1860. Its engineering design and construction are the basis for its importance, and it remains in vehicular use after repointing.","period_of_significance":"1827-1829","architect_builder":"Silas Harry (builder)","architectural_style":"Camelback","criteria":[],"status_note":"Repointed; in vehicular use","vacant_flag":false,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:35.759206-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/88000777.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/88000777/ab334bb3db-800.webp","url_1600":"https://nationalhistoricalregister.com/media/88000777/ab334bb3db-1600.webp","licence":"Public domain","author":"PennDOT","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:McClay%27s_Twin_Bridge_(East).jpg\" rel=\"noopener\">PennDOT</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:McClay%27s_Twin_Bridge_(East).jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71992957","wikipedia":"https://en.wikipedia.org/wiki/McClay%27s_Twin_Bridge_(East)","wikidata":"https://www.wikidata.org/wiki/Q15252508"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/franklin-county/mcclays-twin-bridge-east-88000777/"}