{"nrhp_refnum":"04000178","name":"Lock and Dam No. 18 Historic District","other_names":[],"category":"district","location":{"address":"1.5 mi. N of unnamed cty rd. from Gladstone","address_restricted":false,"city":"Gladstone","county":"Henderson County","state":"IL","lat":40.888947794000046,"lon":-91.02505879734812,"geom_source":"nps_gis"},"listed_date":"2004-03-10","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Transportation","Engineering","Maritime History","Commerce","Conservation","Economics","Politics/Government","Military","Social History"],"significance_levels":["national"],"summary":{"what_it_is":"A 204.98-acre federally owned navigation district at Gladstone, Henderson County, Illinois, made up of a lift lock, a nonnavigable dam and associated resources on the Upper Mississippi River. Most of it was built between 1934 and 1937.","why_significant":"It is part of the Upper Mississippi River 9-Foot Navigation Project and has been in continuous use since September 8, 1937. Its dam has unique submersible, elliptical Tainter gates with girder framing, and it was one of the first two dams in the Rock Island District to use submersible roller gates. It also reflects the project's importance in transportation, commerce, conservation, military and social history.","narrative":"Lock and Dam No. 18 spans the Upper Mississippi River near Gladstone, Illinois, where the river is more than a mile wide. The district covers about 205 acres and includes a lift lock with a 10.5-foot lift, an incomplete auxiliary lock, a central control station, a dam with 13 Tainter gates and three roller gates, long earth dikes and an 11-acre esplanade. Contractors built most of it between 1934 and 1937, and it opened to navigation on September 8, 1937, as the eleventh complex of the 9-foot channel project. It matters for its role in river transportation and for its engineering. The dam's submersible, elliptical Tainter gates use a revised girder frame and are unique, since no others were built. A guard wall added in 1941 and a guide wall extension in 1951 addressed outdraft problems. Later rehabilitation replaced much machinery, yet the lock, dam and setting remain largely as they were in 1948.","period_of_significance":"1934-1948","architect_builder":"Maxon Construction Company, Inc. (lock and central control station); S. A. Healy Construction Company (dam); Rock Island District, U.S. Army Corps of Engineers (design; Edwin E. Abbott signed the dam drawings)","architectural_style":"OTHER: lock and dam; NO STYLE: control station; OTHER: machinery","criteria":[],"status_note":"In continuous use since 1937; the lock and dam were resurfaced and most machinery replaced in-kind in the 1989-1992 rehabilitation, and the components are described as in excellent condition.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:37.18494-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/58/8911/28891158/content/electronic-records/rg-079/NPS_IL/04000178.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/04000178/7541165dfb-800.webp","url_1600":"https://nationalhistoricalregister.com/media/04000178/7541165dfb-1600.webp","licence":"Public domain","author":"US Army Corps of Engineers, Unknown Photographer","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Mississippi_River_Lock_and_Dam_number_18.jpg\" rel=\"noopener\">US Army Corps of Engineers, Unknown Photographer</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Mississippi_River_Lock_and_Dam_number_18.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/28891158","wikipedia":"https://en.wikipedia.org/wiki/Lock_and_Dam_No._18","wikidata":"https://www.wikidata.org/wiki/Q6665264"},"indexable":true,"url":"https://nationalhistoricalregister.com/illinois/henderson-county/lock-and-dam-no-18-historic-district-04000178/"}