{"nrhp_refnum":"83001665","name":"Double-Span Metal Pratt Truss Bridge","other_names":[],"category":"structure","location":{"address":"AuSable St.","address_restricted":false,"city":"Keeseville","county":"Clinton County","state":"NY","lat":44.50033531100007,"lon":-73.48498539599996,"geom_source":"nps_gis"},"listed_date":"1983-05-20","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering"],"significance_levels":["local"],"summary":{"what_it_is":"A double-span wrought-iron Pratt through-truss highway bridge carrying AuSable Street over the AuSable River in Keeseville, between Clinton and Essex Counties, New York. It was built in 1877.","why_significant":"The nomination calls it the oldest surviving metal Pratt truss bridge in New York State and the earliest metal truss bridge in the Adirondack region. It is also a rare surviving example by its manufacturer, Murray Dougal & Company. Its finials, builder's plates and decorative portal bracing remain intact, making it a significant engineering resource and local landmark.","narrative":"Spanning the AuSable River near the southern edge of Keeseville, this wrought-iron bridge links AuSable Street in Clinton County with River Street in Essex County. Built in 1877 by Murray Dougal & Company of Milton, Pennsylvania, to the design of engineer William H. Law, it consists of two identical 107-foot through-truss spans resting on a midstream pier, for a total length of 214 feet and a roadway 16 feet wide. Locally known as the upper bridge, it uses the Pratt configuration, with vertical members in compression and diagonals in tension. The stone pier and abutments have been replaced with concrete, and a steel mesh deck replaced the timber deck in the 1950s. It still carries traffic under a six-ton limit. It is considered the oldest surviving metal Pratt truss bridge in New York State and the earliest metal truss bridge in the Adirondack region. Finials, builder's plates and decorative bracing survive.","period_of_significance":null,"architect_builder":"William H. Law (Engineer); Murray Dougal & Company, Milton, PA","architectural_style":"Pratt truss (wrought iron, pin-connected)","criteria":[],"status_note":"Still used as a vehicular bridge, subject to a six-ton limit; condition described as fair.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:50:42.917283-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_NY/83001665.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/83001665/6f597e1b8d-800.webp","url_1600":"https://nationalhistoricalregister.com/media/83001665/6f597e1b8d-1600.webp","licence":"CC BY-SA 3.0","author":"Mwanner","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Double-Span_Metal_Pratt_Truss_Bridge,_Keeseville,_NY.jpg\" rel=\"noopener\">Mwanner</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:Double-Span_Metal_Pratt_Truss_Bridge,_Keeseville,_NY.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/75312351","wikipedia":"https://en.wikipedia.org/wiki/Double-Span_Metal_Pratt_Truss_Bridge","wikidata":"https://www.wikidata.org/wiki/Q5299577"},"indexable":true,"url":"https://nationalhistoricalregister.com/new-york/clinton-county/double-span-metal-pratt-truss-bridge-83001665/"}