{"nrhp_refnum":"79000378","name":"Ponakin Bridge","other_names":[],"category":"structure","location":{"address":"N of Lancaster on Ponakin Rd.","address_restricted":false,"city":"Lancaster","county":"Worcester County","state":"MA","lat":42.481230107000044,"lon":-71.68523480599998,"geom_source":"nps_gis"},"listed_date":"1979-09-10","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation"],"significance_levels":["national"],"summary":{"what_it_is":"A single-span Post through truss bridge built in 1871 carrying Ponakin Road over the north branch of the Nashua River, north of Lancaster, Worcester County, Massachusetts.","why_significant":"The nomination argues the bridge retains integrity of location, design, setting, materials and workmanship and is tied to major transportation routes and the development of Lancaster. It is described as the only remaining pure version of a Post truss known to the Historic American Engineering Record. With the nearby Atherton Bridge, it forms a unique pair of surviving examples in the country.","narrative":"Ponakin Road crosses the north branch of the Nashua River in Lancaster on a single-span iron Post through truss bridge built in 1871. It spans 100 feet, is 20 feet wide, has eight panels, and rests on granite block abutments. The town hired Watson Manufacturing Company, builders from Paterson, New Jersey, to replace the last of a series of wooden bridges on the site dating to the seventeenth century. The cost was $5,981, and the design followed the patent of civil engineer Simeon S. Post. The bridge once lay on the main route from Lancaster to Lunenburg but now sits on a quiet country road near a 1965 by-pass. It is notable as the only pure example of a Post truss known to the Historic American Engineering Record, and it forms a rare pair with the nearby Atherton Bridge. Town-funded repairs have kept it open to light traffic, with a four-ton limit.","period_of_significance":"1871","architect_builder":"Watson Manufacturing Company","architectural_style":"Post through truss","criteria":[],"status_note":"Town-owned and in use for automobile traffic, with a four-ton load limit that excludes trucks and heavy loads; condition listed as good.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:11:53.536224-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/42/7975/63797542/content/electronic-records/rg-079/NPS_MA/79000378.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/79000378/3a9ba14348-800.webp","url_1600":"https://nationalhistoricalregister.com/media/79000378/3a9ba14348-1600.webp","licence":"Public domain","author":"Jet Lowe","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Ponakin_Bridge.jpg\" rel=\"noopener\">Jet Lowe</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Ponakin_Bridge.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/63797542","wikipedia":"https://en.wikipedia.org/wiki/Ponakin_Bridge","wikidata":"https://www.wikidata.org/wiki/Q7227555"},"indexable":true,"url":"https://nationalhistoricalregister.com/massachusetts/worcester-county/ponakin-bridge-79000378/"}