{"nrhp_refnum":"80003400","name":"Davis Island Lock and Dam Site","other_names":[],"category":"site","location":{"address":"Off PA 65","address_restricted":false,"city":"Avalon","county":"Allegheny County","state":"PA","lat":40.493013750000046,"lon":-80.06533349399996,"geom_source":"nps_gis"},"listed_date":"1980-08-29","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Industry","Engineering","Transportation"],"significance_levels":["national"],"summary":{"what_it_is":"A former navigation lock and movable dam site on the Ohio River at Davis Island in Avalon, Allegheny County, Pennsylvania, built by the Corps of Engineers between 1878 and 1885. The landward cutstone lockwall remains visible while the dam and riverward lockwall were removed in 1922.","why_significant":"The project is argued to be significant for its engineering innovations, including the first rolling lock gates on the Ohio River, a large Chanoine wicket dam, and what was then the widest lock chamber in the world. Its design was repeated at about 50 dams along the Ohio River, which supported river commerce and the industrial development of the Port of Pittsburgh.","narrative":"Davis Island Lock and Dam is a former navigation lock and movable dam on the Ohio River at Avalon, Allegheny County, Pennsylvania. Construction by the Corps of Engineers began on July 30, 1878, and was completed on October 7, 1885, at a cost of $940,832.31. The lock chamber measured 600 feet long and 110 feet wide, larger than the later Panama Canal locks. Its rolling lock gates, made of wooden Howe trusses on iron wheels, ran into recesses like railroad cars, a design chosen because available materials lacked the rigidity needed for mitered gates across such a wide chamber. The dam used 305 Chanoine wickets, a French design modified by the Corps. The project proved successful enough that about 50 similar dams were built along the Ohio River by 1929. It was replaced by the Emsworth Locks and Dam in 1922, after which the dam and riverward lockwall were removed. The massive cutstone landward lockwall remains in place.","period_of_significance":"1878-1885","architect_builder":"Corps of Engineers","architectural_style":null,"criteria":["A","C"],"status_note":"Dam and riverward lockwall removed in 1922; landward lockwall remains in place and is visible except during floods.","vacant_flag":null,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:32.345633-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/80003400.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/80003400/20314cfdb2-800.webp","url_1600":"https://nationalhistoricalregister.com/media/80003400/20314cfdb2-1600.webp","licence":"Public domain","author":"Nyttend","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Davis_Island_dam_site_from_Fleming_Park_Bridge.jpg\" rel=\"noopener\">Nyttend</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Davis_Island_dam_site_from_Fleming_Park_Bridge.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71994557","wikipedia":"https://en.wikipedia.org/wiki/Davis_Island_Lock_and_Dam_Site","wikidata":"https://www.wikidata.org/wiki/Q5241917"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/allegheny-county/davis-island-lock-and-dam-site-80003400/"}