{"nrhp_refnum":"00000403","name":"Allegheny River Lock and Dam No. 9","other_names":[],"category":"structure","location":{"address":"Terminus of PA 1004, 0.2 mi. N of T488","address_restricted":false,"city":"Widnoon","county":"Armstrong County","state":"PA","lat":40.95367022850007,"lon":-79.54630696690947,"geom_source":"nps_gis"},"listed_date":"2000-04-21","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Transportation","Maritime History","Architecture","Engineering"],"significance_levels":["state"],"summary":{"what_it_is":"A U.S. Army Corps of Engineers navigation facility on the Allegheny River near Widnoon in Armstrong County, Pennsylvania, comprising a lock, dam, esplanade, gauging station, operations building and locktenders' houses. It was constructed in 1937-1938.","why_significant":"The nomination argues the lock and dam are significant for their role in the Allegheny River slackwater navigation system, giving barge access to limestone quarries near East Brady. It also argues they are a representative example of lock and dam construction of 1937-1938, retaining original appearance, machinery and function.","narrative":"Lock and Dam No. 9 sits on the east side of the Allegheny River in a rural setting, and it was built by the U.S. Army Corps of Engineers between 1937 and 1938. York Engineering and Construction served as contractor. The 56-by-360-foot lock lifts vessels 22 feet, the highest lift on the river, and its steel miter gates close against a concrete sill. The 918-foot dam rests on bedrock and carries water across its full length without a spillway. A terrace of river-dredged material extends about 0.6 miles downstream to provide a nine-foot channel to the lower gate. The lock was designed to give slackwater navigation to limestone quarries near East Brady, extending the navigation system upstream. Its operating machinery, powered by turbines, has been largely retained, and the lock is regarded as a representative example of the period's standard lock and dam design.","period_of_significance":"1903-1948","architect_builder":"York Engineering and Construction (contractor)","architectural_style":"Late 19th and early 20th century revival","criteria":["A","C"],"status_note":"In operation; the hydroelectric plant was added in 1990, the operations building was pargeted circa 1990, and the heating system was converted to gas in 1964.","vacant_flag":false,"machine_generated":true,"model":"claude-haiku-5-5","prompt_version":"v1.1-2026-10-29","generated_at":"2026-10-29 17:11:36.849689-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_PA/00000403.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/00000403/bb2d5269c6-800.webp","url_1600":"https://nationalhistoricalregister.com/media/00000403/bb2d5269c6-1600.webp","licence":"CC BY-SA 3.0","author":"Generic1139","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Allegheny_River_Lock_and_Dam_No._9.jpg\" rel=\"noopener\">Generic1139</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:Allegheny_River_Lock_and_Dam_No._9.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71992266","wikipedia":"https://en.wikipedia.org/wiki/Allegheny_River_Lock_and_Dam_No._9","wikidata":"https://www.wikidata.org/wiki/Q4731342"},"indexable":true,"url":"https://nationalhistoricalregister.com/pennsylvania/armstrong-county/allegheny-river-lock-and-dam-no-9-00000403/"}