{"nrhp_refnum":"98000984","name":"Cave-In-Rock","other_names":["Big Cave","Rock and Cave"],"category":"site","location":{"address":"0.5 mi N of the town of Cave-In-Rock","address_restricted":false,"city":"Cave-In-Rock","county":"Hardin County","state":"IL","lat":37.46735557000005,"lon":-88.15865573499997,"geom_source":"nps_gis"},"listed_date":"1998-08-06","is_nhl":false,"nhl_designated_date":null,"areas_of_significance":["Military"],"significance_levels":["local"],"summary":{"what_it_is":"A natural limestone cave set into a 60-foot bluff on the Ohio River in Cave-In-Rock State Park, Hardin County, Illinois, nominated as a site under a Civil War multiple property listing.","why_significant":"The nomination argues the cave is locally significant for Civil War associations. It sheltered Unionist refugees in late 1861, who were seen by Brig. Gen. Ulysses S. Grant and moved to Paducah and Cairo. Stone was quarried nearby for the Federal defenses at Cairo, and the site was the staging point for a Federal raid on Caseyville.","narrative":"Cave-In-Rock is a natural limestone cave opening onto the Ohio River in Hardin County, Illinois, within the 150-acre state park of the same name. The arched mouth is about fifty-five feet wide, and the cavern runs back roughly 160 feet. Long known as a navigational landmark and as a hideout associated with river pirates, it also played a part in the Civil War. In late 1861, Unionist refugees from Kentucky took shelter in and around the cave, and Brig. Gen. Ulysses S. Grant saw their condition and had them moved to Paducah and Cairo. A Federal camp was in place there by November 29, 1861, and soldiers spent ten days quarrying stone for the defenses at Cairo. The cave also served as the jumping-off point for a Federal raid on Caseyville, Kentucky. These wartime events are the basis for its local significance, with a period of 1861 to 1864.","period_of_significance":"1861-1864","architect_builder":null,"architectural_style":"Other - Natural Cave","criteria":["A"],"status_note":"Part of Cave-In-Rock State Park, used for outdoor recreation; graffiti is regularly cleaned from the cave.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:37.798773-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/54/8911/28891154/content/electronic-records/rg-079/NPS_IL/98000984.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/98000984/41ec277485-800.webp","url_1600":"https://nationalhistoricalregister.com/media/98000984/41ec277485-1600.webp","licence":"CC BY-SA 4.0","author":"Daniel Schwen","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Cave-in-rock_IL.jpg\" rel=\"noopener\">Daniel Schwen</a>, <a href=\"https://creativecommons.org/licenses/by-sa/4.0\" rel=\"license noopener\">CC BY-SA 4.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Cave-in-rock_IL.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/28891154","wikipedia":"https://en.wikipedia.org/wiki/Cave-in-Rock_State_Park","wikidata":"https://www.wikidata.org/wiki/Q5054883"},"indexable":true,"url":"https://nationalhistoricalregister.com/illinois/hardin-county/cave-in-rock-98000984/"}