{"nrhp_refnum":"66000899","name":"Cahokia Mounds","other_names":["Monks Mounds"],"category":"site","location":{"address":"7850 Collinsville Rd., Cahokia Mounds State Park","address_restricted":false,"city":"Collinsville","county":"St. Clair County","state":"IL","lat":38.65991103150006,"lon":-90.07976265195603,"geom_source":"nps_gis"},"listed_date":"1966-10-15","is_nhl":true,"nhl_designated_date":"1964-07-19","areas_of_significance":["Prehistoric"],"significance_levels":["national"],"summary":{"what_it_is":"A prehistoric Mississippian archaeological site of over 100 earthen mounds, centered on Monks Mound, in the American Bottoms east of St. Louis near Collinsville, Illinois, covering about 4,000 acres. Occupation ran from roughly 800 to 1500 A.D.","why_significant":"The form describes Cahokia as the largest Mississippian Period community in eastern North America, with a planned rectangular layout, a timber palisade and woodhenges. It may have housed 40,000 people at its peak and served as a major trade center. It is called of preeminent importance for studying prehistoric urbanism.","narrative":"Cahokia Mounds is a vast Mississippian-era site east of St. Louis, in the flood plain known as the American Bottoms. Its centerpiece, Monks Mound, covers about 15 acres and rises in four terraces to roughly 100 feet. More than one hundred smaller mounds served as platforms for temples and residences, as burial places, or as markers of the city's limits. The settlement followed a regular north-south and east-west plan, included houses grouped around plazas, and was ringed in its core by a log palisade. Circles of posts called woodhenges are interpreted as calendars. Occupied from about 800 to 1500 A.D., the city may have held 40,000 people around 1150 and acted as a major trading hub, with goods arriving from the Ozarks, Lake Superior, the Gulf Coast and beyond. The nomination treats it as unique and important for understanding early urban life in North America. Part of the site is now a state park, though roads, an interstate and development have intruded on the remainder.","period_of_significance":"approximately 800-1500 A.D.","architect_builder":null,"architectural_style":null,"criteria":[],"status_note":"About 650 of roughly 4,000 acres are state-owned and maintained as a park with a museum and a reconstructed section of palisade. Other mounds are privately owned, and some have been nearly obliterated by cultivation or urban expansion.","vacant_flag":null,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:55:35.635274-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/opastorage/live/21/8916/28891621/content/electronic-records/rg-079/NPS_IL/66000899_NHL.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/66000899/bddc21e637-800.webp","url_1600":"https://nationalhistoricalregister.com/media/66000899/bddc21e637-1600.webp","licence":"CC BY 2.0","author":"Thank You (24 Millions ) views","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:Cahokia_Mounds_--_UNESCO_reconstruction.jpg\" rel=\"noopener\">Thank You (24 Millions ) views</a>, <a href=\"https://creativecommons.org/licenses/by/2.0\" rel=\"license noopener\">CC BY 2.0</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:Cahokia_Mounds_--_UNESCO_reconstruction.jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/28891621","wikipedia":"https://en.wikipedia.org/wiki/Cahokia","wikidata":"https://www.wikidata.org/wiki/Q333661"},"indexable":true,"url":"https://nationalhistoricalregister.com/illinois/st-clair-county/cahokia-mounds-66000899/"}