{"nrhp_refnum":"79000377","name":"Atherton Bridge","other_names":[],"category":"structure","location":{"address":"Bolton Rd.","address_restricted":false,"city":"Lancaster","county":"Worcester County","state":"MA","lat":42.44471181200004,"lon":-71.67187936799996,"geom_source":"nps_gis"},"listed_date":"1979-09-19","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation"],"significance_levels":["national"],"summary":{"what_it_is":"A single-span pony truss bridge built in 1870 on Bolton Road in Lancaster, Massachusetts, carrying the road over the Nashua River about 3/4 mile east of South Lancaster.","why_significant":"It was Lancaster's first iron bridge and sits on one of the town's main roads into Lancaster. It uses many features of the Post truss and is one of only two surviving examples known to the Historic American Engineering Record, the other being the nearby Ponakin Bridge. Together the two bridges represent an important era in American engineering.","narrative":"Atherton Bridge is a single-span iron pony truss built in 1870 where Bolton Road crosses the Nashua River in Lancaster, Massachusetts. The town paid $4,000 for it, and it was the first iron bridge in Lancaster. The structure has eight truss panels, a 72-foot span and an 18-foot width, and it rests on large granite block abutments. It is not a patented Post truss, but it borrows many Post features, including diagonal compression members that incline toward the center, riveted dual tension rods and Phoenix Columns. The bridge was named for the nearby Atherton family, descendants of an early signer of Lancaster's 1653 incorporation petition. It is valued as one of only two surviving examples of this truss type known to the Historic American Engineering Record, along with the nearby Ponakin Bridge. Several compression members have worked loose from their fittings, and the bridge has been closed to traffic for several years. It sits in open flood plain.","period_of_significance":"1800-1899","architect_builder":null,"architectural_style":"Pony truss with Post truss features","criteria":[],"status_note":"Closed to traffic for several years because several compression members are loose from their fittings; listed in good condition and owned by the town.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:11:54.153364-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/40/7975/63797540/content/electronic-records/rg-079/NPS_MA/79000377.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/79000377/d615d3662b-800.webp","url_1600":"https://nationalhistoricalregister.com/media/79000377/d615d3662b-1600.webp","licence":"Public domain","author":"Jet Lowe","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Atherton_Bridge.jpg\" rel=\"noopener\">Jet Lowe</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Atherton_Bridge.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/63797540","wikipedia":"https://en.wikipedia.org/wiki/Atherton_Bridge","wikidata":"https://www.wikidata.org/wiki/Q4813590"},"indexable":true,"url":"https://nationalhistoricalregister.com/massachusetts/worcester-county/atherton-bridge-79000377/"}