{"nrhp_refnum":"81000117","name":"Granite Keystone Bridge","other_names":["Granite Bridge"],"category":"structure","location":{"address":"Granite St.","address_restricted":false,"city":"Rockport","county":"Essex County","state":"MA","lat":42.66706186600004,"lon":-70.62535038999994,"geom_source":"nps_gis"},"listed_date":"1981-08-27","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Industry","Engineering"],"significance_levels":["local"],"summary":{"what_it_is":"A single-arch granite bridge built in 1872 carrying Granite Street (Route 127) over the \"Cut\" between Rockport and Pigeon Cove, Massachusetts. It was built of granite from the adjacent quarry under the direction of Jonathan Pratt of Quincy.","why_significant":"The nomination argues the bridge is a reminder of Rockport's early industrial base, tied to the granite quarrying business. It is also described as a locally significant accomplishment of late-nineteenth century civil engineering. It retains integrity of location, design, setting, materials and workmanship.","narrative":"Carrying Granite Street (Route 127) between Rockport and Pigeon Cove, this single-arch bridge was built in 1872 of dressed, coursed granite taken from the neighboring quarry. Its arch spans 65 feet and the deck is 32 feet wide. The Rockport Granite Company needed a quick way to move stone from the quarry to its piers, so a cut was dug beneath the road around 1868 and the bridge was raised over it. Jonathan Pratt of Quincy, an experienced builder of stone arches, directed the work, which took about eleven weeks. Contemporary newspapers called it one of the largest stone arches in the state. The bridge remains in original condition and still serves traffic. It was listed as a reminder of Rockport's granite industry, which supplied stone to cities along the eastern and southern coasts, and as a local example of nineteenth-century civil engineering. The nomination covers only the bridge itself.","period_of_significance":"1872","architect_builder":"Jonathan Pratt of Quincy, Massachusetts","architectural_style":null,"criteria":["A","C"],"status_note":"Described as unaltered, in good condition, on its original site, and still functional as part of Route 127; the form checks public ownership and occupied status.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:11:54.205872-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/29/7950/63795029/content/electronic-records/rg-079/NPS_MA/81000117.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/81000117/1c3460efe2-800.webp","url_1600":"https://nationalhistoricalregister.com/media/81000117/1c3460efe2-1600.webp","licence":"CC BY-SA 3.0","author":"Pi.1415926535","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Granite_Keystone_Bridge_from_the_west,_July_2016.JPG\" rel=\"noopener\">Pi.1415926535</a>, <a href=\"https://creativecommons.org/licenses/by-sa/3.0\" rel=\"license noopener\">CC BY-SA 3.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Granite_Keystone_Bridge_from_the_west,_July_2016.JPG"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/63795029","wikipedia":"https://en.wikipedia.org/wiki/Granite_Keystone_Bridge","wikidata":"https://www.wikidata.org/wiki/Q5595884"},"indexable":true,"url":"https://nationalhistoricalregister.com/massachusetts/essex-county/granite-keystone-bridge-81000117/"}