{"nrhp_refnum":"80003509","name":"Mercer's Mill Covered Bridge","other_names":[],"category":"structure","location":{"address":"NE of Christiana","address_restricted":false,"city":"Christiana","county":"Lancaster County","state":"PA","lat":39.931462632000034,"lon":-75.98132027799994,"geom_source":"nps_gis"},"listed_date":"1980-12-11","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Engineering","Transportation"],"significance_levels":["state"],"summary":{"what_it_is":"A Burr truss covered bridge carrying T976 across Octoraro Creek near Christiana, spanning the boundary of West Fallowfield Township in Chester County and Sadsbury Township in Lancaster County. It was built in 1880 by B. J. Carter.","why_significant":"The nomination treats the bridge as one of a group of nineteenth-century covered bridges in Lancaster County that together illustrate wood frame construction, a theme used for the multiple-resource submission. It is described as being in good condition, with vertical plank siding and horizontal siding in the portals.","narrative":"Built in 1880 by B. J. Carter, Mercer's Mill Covered Bridge is a Burr truss span carrying a township road over Octoraro Creek near Christiana. The bridge crosses the line between West Fallowfield Township in Chester County and Sadsbury Township in Lancaster County, and is owned jointly by the two counties. Its end posts are 85 feet long, and it has vertical plank siding along its sides with horizontal siding in the portals. The nomination places it within a thematic group of covered bridges in Lancaster County that show wood frame construction practice in the nineteenth century. Reviewers found the bridge in good condition and considered it a suitable example of the group, though they asked for boundaries that would take in the abutments more fully.","period_of_significance":null,"architect_builder":"B. J. Carter (builder)","architectural_style":null,"criteria":[],"status_note":"Condition described as good","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:34.167801-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/80003509.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/80003509/928ff29af7-800.webp","url_1600":"https://nationalhistoricalregister.com/media/80003509/928ff29af7-1600.webp","licence":"CC BY-SA 2.5","author":"Photo by and (c)2006 Derek Ramsey (Ram-Man)","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Mercer%27s_Mill_Covered_Bridge_Side_3000px.jpg\" rel=\"noopener\">Photo by and (c)2006 Derek Ramsey (Ram-Man)</a>, <a href=\"https://creativecommons.org/licenses/by-sa/2.5\" rel=\"license noopener\">CC BY-SA 2.5</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Mercer%27s_Mill_Covered_Bridge_Side_3000px.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71993299","wikipedia":"https://en.wikipedia.org/wiki/Mercer%27s_Mill_Covered_Bridge","wikidata":"https://www.wikidata.org/wiki/Q6818245"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/lancaster-county/mercers-mill-covered-bridge-80003509/"}