{"nrhp_refnum":"97001251","name":"Hanging Rock","other_names":["Overhanging Rock"],"category":"site","location":{"address":"1144 S. Gulph Rd.","address_restricted":false,"city":"Upper Marion Township","county":"Montgomery County","state":"PA","lat":40.06549276800007,"lon":-75.34156050399997,"geom_source":"nps_gis"},"listed_date":"1997-12-24","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Conservation"],"significance_levels":["local"],"summary":{"what_it_is":"The Hanging Rock is a large natural outcropping of metamorphic phyllite beside South Gulph Road in Gulph Mills, Upper Merion Township, Montgomery County, Pennsylvania. The nominated property is a small parcel of about 24,000 square feet containing the rock.","why_significant":"The nomination argues the rock is significant for its long association with the Gulph Road and with the Continental Army's march to Valley Forge in December 1777, and for the local efforts that repeatedly saved it from removal from 1917 onward. It is also presented as a commemorative property tied to the American Revolution.","narrative":"Beside South Gulph Road in Gulph Mills, Upper Merion Township, a natural outcropping of metamorphic phyllite rises above a narrow valley cut by Gulph Creek. The rock overhangs the roadway by about eight feet, and the road itself was formally established as a public road in 1711 and 1712. A small parcel of roughly 24,000 square feet containing the rock was deeded to the Valley Forge Historical Society in 1924 for perpetual preservation. The nomination ties the site to the Continental Army's passage beneath the rock on December 19, 1777, during the march to Valley Forge, and to the later Revolutionary-era traffic through the pass. Repeated threats of removal, beginning in 1917, prompted local protests that stopped the work, and the rock came to be regarded as a local landmark and commemorative memorial to the Revolution. Dynamite holes drilled in 1917 and 1954 and vehicle strikes have changed its shape over time.","period_of_significance":"1917-1924","architect_builder":null,"architectural_style":null,"criteria":["A"],"status_note":"The rock remains in place beside the roadway; its overhang has been reduced over time by vehicle strikes and erosion, and it was threatened with removal in 1917, 1954 and the 1970s.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:13:38.563122-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/97001251.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/97001251/fa5ec65b34-800.webp","url_1600":"https://nationalhistoricalregister.com/media/97001251/fa5ec65b34-1600.webp","licence":"Public domain","author":"John Thomson Faris","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Gulph_Rock.JPG\" rel=\"noopener\">John Thomson Faris</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Gulph_Rock.JPG"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71995725","wikipedia":"https://en.wikipedia.org/wiki/Hanging_Rock_(Upper_Merion_Township,_Pennsylvania)","wikidata":"https://www.wikidata.org/wiki/Q5648010"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/montgomery-county/hanging-rock-97001251/"}