{"nrhp_refnum":"93000720","name":"Dauphin County Bridge No. 27","other_names":["Seaman Bridge"],"category":"structure","location":{"address":"Deibler's Dam Rd. (Mahantango Creek Rd.) across Mahantango Cr. (Mifflin and Lower Mahanoy Townships)","address_restricted":false,"city":"Pillow","county":"Dauphin County","state":"PA","lat":40.634857984000064,"lon":-76.85605798499995,"geom_source":"nps_gis"},"listed_date":"1993-08-02","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering"],"significance_levels":["local"],"summary":{"what_it_is":"A metal truss bridge spanning Mahantango Creek between Mifflin Township, Dauphin County and Lower Mahanoy Township, Northumberland County, Pennsylvania. It was built in 1896 by the Chambersburg Bridge Company and is also known as Seaman Bridge.","why_significant":"The bridge is presented as an excellent example of a late nineteenth century metal truss bridge, notable for its 162.5-foot span. Its truss design is described as a variation of the Baltimore truss, with the vertical members loaded in reverse of the usual arrangement. It is also argued to be important to nearby residents, who would face long detours if it were unavailable for access.","narrative":"Built in 1896 by the Chambersburg Bridge Company, this metal truss bridge crosses Mahantango Creek between Mifflin Township in Dauphin County and Lower Mahanoy Township in Northumberland County. It measures 162.5 feet long, with ten 16-foot-3-inch panels, and rests on stone abutments. Its design is a variant of the Baltimore truss. Its upper built-up verticals are used in compression and its lower verticals in tension, the reverse of the usual Baltimore arrangement, and the document treats this as the reason for its significance. The bridge survived the 1972 flood undamaged. It was closed to vehicles in 1983 and to pedestrians in March 1992. Nearby residents of a cul-de-sac relied on it for emergency egress, and its closure forces a 2.5-mile detour. The document describes its historic integrity as excellent and recommends rehabilitation.","period_of_significance":"1896","architect_builder":"Chambersburg Bridge Company (builder)","architectural_style":"Metal truss bridge; variant of the Baltimore truss type","criteria":["C"],"status_note":"Closed to vehicular traffic since 1983 and restricted to both vehicles and pedestrians; pedestrian crossing ended March 1992.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:35.92248-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/93000720.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/93000720/7f81aa1b56-800.webp","url_1600":"https://nationalhistoricalregister.com/media/93000720/7f81aa1b56-1600.webp","licence":"CC BY-SA 4.0","author":"JERRYE &amp; ROY KLOTZ, M.D.","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Deibler%27s_Mill_bridge_over_Mahantango_Creek.jpg\" rel=\"noopener\">JERRYE &amp;amp; ROY KLOTZ, M.D.</a>, <a href=\"https://creativecommons.org/licenses/by-sa/4.0\" rel=\"license noopener\">CC BY-SA 4.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Deibler%27s_Mill_bridge_over_Mahantango_Creek.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71996535","wikipedia":"https://en.wikipedia.org/wiki/Dauphin_County_Bridge_No._27","wikidata":"https://www.wikidata.org/wiki/Q5228066"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/dauphin-county/dauphin-county-bridge-no-27-93000720/"}