{"nrhp_refnum":"66000602","name":"Serpent Mound","other_names":["Great Serpent Mound State Memorial"],"category":"site","location":{"address":"5 mi. NW of Locust Grove on OH 73","address_restricted":false,"city":"Locust Grove","county":"Adams County","state":"OH","lat":39.02465924750007,"lon":-83.43071112467283,"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":"Serpent Mound is a prehistoric earthen effigy site on the east bluffs of Brush Creek near Locust Grove, Adams County, Ohio. It includes a giant serpent-shaped embankment and nearby burial mounds, stone graves and fireplace areas, and is attributed to the Adena period.","why_significant":"The nomination calls it one of the few effigy mounds in Ohio and the largest and finest serpent effigy in the United States. Associated mounds and burials point to an Adena date of about 1000 B.C. to 200 A.D. Excavations in 1886 yielded information about the effigy's construction and about the lifestyle and burial practices of its builders.","narrative":"Serpent Mound is an earthen effigy on a hilltop spur above Brush Creek near Locust Grove, Ohio. The embankment represents a serpent uncoiling. It follows the curve of the land for 737 feet and measures 1,254 feet along its windings, with seven deep curves, a coiled tail and open jaws reaching toward an oval mound. It stands 4 to 5 feet high and averages 20 feet wide. Nearby are a conical burial mound, a smaller burial mound, an oval mound and a cluster of stone graves and fireplace areas. Squier and Davis described the site in 1848, and Frederic Putnam excavated and restored it after 1886. The conical mound shows Adena traits, which is why the effigy is attributed to the Adena period, roughly 1000 B.C. to 200 A.D. The mound is described as the largest and finest serpent effigy in the United States. Builders outlined it with stone and clay, then covered it with dirt. The purpose of the effigy remains uncertain.","period_of_significance":"approximately 1000 B.C. - 200 A.D.","architect_builder":null,"architectural_style":null,"criteria":[],"status_note":"Condition marked good and altered, in public ownership and used as a park and museum. Intrusions include an access road, a parking lot and a steel observation tower. A museum, barn, residence, service building and shelter lie within the boundary but are not part of the landmark.","vacant_flag":false,"machine_generated":true,"model":"claude-sonnet-5-5","prompt_version":"v1.0-2026-10-29","generated_at":"2026-10-29 02:53:10.358471-05","source_pdf":"https://s3.amazonaws.com/NARAprodstorage/lz/electronic-records/rg-079/NPS_OH/66000602_NHL.pdf"},"photo":{"url_800":"https://nationalhistoricalregister.com/media/66000602/35fa20a041-800.webp","url_1600":"https://nationalhistoricalregister.com/media/66000602/35fa20a041-1600.webp","licence":"No restrictions","author":"The British Library","credit_html":"<a href=\"https://commons.wikimedia.org/wiki/File:26_of_%27A_School_History_of_the_United_States_...Serpent_Mound_in_Ohio%22%27_no_cap_(11303842305)_(cropped).jpg\" rel=\"noopener\">The British Library</a>, <a href=\"https://www.flickr.com/commons/usage/\" rel=\"license noopener\">No restrictions</a>, via Wikimedia Commons","source_page":"https://commons.wikimedia.org/wiki/File:26_of_%27A_School_History_of_the_United_States_...Serpent_Mound_in_Ohio%22%27_no_cap_(11303842305)_(cropped).jpg"},"district":null,"sources":{"nps_snapshot_date":"2026-05-22","nara_catalog":"https://catalog.archives.gov/id/71986437","wikipedia":"https://en.wikipedia.org/wiki/Serpent_Mound","wikidata":"https://www.wikidata.org/wiki/Q968802"},"indexable":true,"url":"https://nationalhistoricalregister.com/ohio/adams-county/serpent-mound-66000602/"}