{"nrhp_refnum":"77000981","name":"Hadley Parabolic Bridge","other_names":[],"category":"site","location":{"address":"CR 1","address_restricted":false,"city":"Hadley","county":"Saratoga County","state":"NY","lat":43.31392050000005,"lon":-73.84499404299999,"geom_source":"nps_gis"},"listed_date":"1977-03-25","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation","Invention"],"significance_levels":["state"],"summary":{"what_it_is":"A two-span iron highway truss bridge carrying Corinth Road (Saratoga County Route) over the Sacandaga River at Hadley, Saratoga County, New York. It was erected by the Town of Hadley in 1895 and built by the Berlin Iron Bridge Co.","why_significant":"The nomination calls it the only known surviving semi-deck lenticular iron truss bridge in New York State. Its larger span uses the lenticular or \"parabolic\" truss patented by William O. Douglas in 1878 and 1885, a design that fell out of use after a brief period of popularity. It is also an important example of late nineteenth-century iron bridge-building and transportation technology.","narrative":"Spanning a deep, wooded ravine over the Sacandaga River, this iron bridge carries Corinth Road between Hadley and its neighbor across the water. Built in 1895 by the Berlin Iron Bridge Company for the Town of Hadley at a cost of $6,000, it has an overall length of 181 feet and rests on rough-cut stone abutments and a single pier. A short pony truss meets a 136-foot lenticular truss, a design patented by engineer William O. Douglas of Binghamton in 1878 and 1885. Such bridges were once common across New York and New England, but the Douglas truss proved too flexible and was made for only about fifteen years. This semi-deck example is the only one known to survive in the state. The timber deck was later replaced, and in 1972 the structure was braced with steel cables and narrowed to fourteen and a half feet. It still serves light vehicles.","period_of_significance":"1800-1899 (specific date 1895)","architect_builder":"Berlin Iron Bridge Co.","architectural_style":null,"criteria":[],"status_note":"Open to vehicular traffic of three tons or less after reinforcement in 1972; owned by the Town of Hadley and listed as occupied and in use as a transportation structure.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:50:38.951603-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_NY/77000981.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/77000981/176f5f4c03-800.webp","url_1600":"https://nationalhistoricalregister.com/media/77000981/176f5f4c03-1600.webp","licence":"CC BY-SA 2.0","author":"Doug Kerr from now in Binghamton, NY. Edited and cropped by Daniel Case","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Hadley_Bow_Bridge.jpg\" rel=\"noopener\">Doug Kerr from now in Binghamton, NY. Edited and cropped by Daniel Case</a>, <a href=\"https://creativecommons.org/licenses/by-sa/2.0\" rel=\"license noopener\">CC BY-SA 2.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Hadley_Bow_Bridge.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/75321588","wikipedia":"https://en.wikipedia.org/wiki/Hadley_Parabolic_Bridge","wikidata":"https://www.wikidata.org/wiki/Q5637981"},"indexable":true,"url":"https://nationalhistoricalregister.com/new-york/saratoga-county/hadley-parabolic-bridge-77000981/"}