{"nrhp_refnum":"04000175","name":"Lock and Dam No. 15 Historic District","other_names":[],"category":"district","location":{"address":"NW of Rodman Ave., Twd., NW tip Arsenal Island","address_restricted":false,"city":"Rock Island","county":"Rock Island County","state":"IL","lat":41.51798571000006,"lon":-90.56431442899998,"geom_source":"nps_gis"},"listed_date":"2004-03-10","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Transportation","Engineering","Maritime History","Social History","Commerce","Conservation","Economics","Military","Politics/Government"],"significance_levels":["national"],"summary":{"what_it_is":"A 359.02-acre federal navigation district at Rock Island, Illinois, spanning the Upper Mississippi River from the northwest tip of Arsenal Island to the Iowa shore. It holds twin locks, a roller-gate dam, a power house, and the Rock Island Arsenal Bridge, built mainly 1931-1934, with the bridge dating to 1895-1896.","why_significant":"The district is part of the Upper Mississippi River 9-Foot Navigation Project and began operating on March 7, 1934. It is one of only three complexes in the project built with a completed, operable auxiliary lock. It also incorporates the 1895-1896 Rock Island Arsenal Bridge, whose swing span pier is encased in the lock wall.","narrative":"Lock and Dam No. 15 crosses the Upper Mississippi River at the foot of the Rock Island Rapids, linking Arsenal Island in Illinois with the Iowa shore. The 359-acre district contains two navigation locks, each with a 16-foot lift, a dam of eleven roller gates, a hydroelectric power house, a storage house, an Iowa-side seawall and intercepting sewer, and the double-deck Rock Island Arsenal Bridge. Contractors built most of the complex between 1931 and 1934, and it went into service on March 7, 1934. The bridge dates to 1895-1896 and its swing span pier is encased in the wall between the locks. The complex is unusual because it had a completed auxiliary lock, as only two other complexes in the project did. A major rehabilitation in 1993 resurfaced the structures and replaced much machinery in kind, but the district retains its location, design, setting, and overall character. It remains in continuous use as part of the 9-Foot Navigation Project.","period_of_significance":null,"architect_builder":"Contractors: Merritt-Chapman and Whitney Corporation (locks), Collier Construction Company (machinery and electrical system), S. A. Healy Company (dam and power house), McKeown Brothers Company (storage house), Steven A. Healy (Iowa seawall and sewer); contract drawings signed by Lenvick Ylvisaker of the UMVD","architectural_style":"OTHER: lock and dam; OTHER: Pratt truss; OTHER: Baltimore truss; OTHER: camelback trough-truss; NO STYLE: power house","criteria":[],"status_note":"In continuous use since March 7, 1934; the locks and dam underwent a major rehabilitation in 1993 and are described as in excellent condition, though not all original architectural details survive.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:37.509178-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/26/8914/28891426/content/electronic-records/rg-079/NPS_IL/04000175.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/04000175/fc10d23562-800.webp","url_1600":"https://nationalhistoricalregister.com/media/04000175/fc10d23562-1600.webp","licence":"Public domain","author":"US Army Corps of Engineers, Carol Arney","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Mississippi_River_Lock_and_Dam_number_15.jpg\" rel=\"noopener\">US Army Corps of Engineers, Carol Arney</a>, Public domain, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Mississippi_River_Lock_and_Dam_number_15.jpg"},"district":{"nrhp_refnum":"69000057","name":"Rock Island Arsenal","url":"https://nationalhistoricalregister.com/districts/illinois/rock-island-arsenal-69000057/"},"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/28891426","wikipedia":"https://en.wikipedia.org/wiki/Lock_and_Dam_No._15","wikidata":"https://www.wikidata.org/wiki/Q1867483"},"indexable":true,"url":"https://nationalhistoricalregister.com/illinois/rock-island-county/lock-and-dam-no-15-historic-district-04000175/"}