Serpent Mound

At a glance

Overview

Serpent Mound is an earthen effigy of a snake with a coiled tail and an oval at its open jaws, laid along a bluff above Ohio Brush Creek in Bratton Township, northern Adams County. It is roughly a quarter mile long if stretched out and about three to six feet high, and it sits inside the Serpent Mound crater, a deeply eroded impact structure hundreds of millions of years old. American Indians built it, but archaeologists still disagree on when: radiocarbon dates published in 1996 pointed to the Fort Ancient culture around A.D. 1070, while cores taken in 2011 and published in 2014 pointed to the Adena culture around 300 B.C. Squier and Davis first published it in 1848; Harvard archaeologist Frederic Ward Putnam, with money raised largely by Boston women led by Alice Fletcher, bought it in June 1887, excavated and restored it, and Harvard gave it to the Ohio State Archaeological and Historical Society in 1900. It is a National Historic Landmark owned and run by the Ohio History Connection and remains on the U.S. Tentative List for the UNESCO World Heritage List.

The U.S. Tentative List entry, submitted on January 30, 2008, calls it the largest documented surviving prehistoric effigy mound in the world, 1.2 to 1.5 meters high and 6 to 7.6 meters wide, and dates it to the Fort Ancient culture about 1120 CE. The Ohio History Connection's own site page is more cautious, saying more work is needed to clarify its age.

The name

Named for its shape. Squier and Davis called it 'the Great Serpent' in their 1848 survey, describing a serpent whose body winds back from the point of the hill 'in graceful undulations, terminating in a triple coil at the tail.' The surrounding impact crater was later named after the mound. (source) Squier and Davis placed it on Brush Creek at a spot locally called the 'Three Forks,' on a crescent-shaped spur 150 feet above the water.

Native American history

The effigy was built by American Indians; which culture is disputed (see stories). The Ohio History Connection says three burial mounds stand nearby, two built by the Adena culture (800 B.C.-A.D. 100) and one by the Fort Ancient culture (A.D. 1000-1650). Putnam's 1887-1889 excavations dug through the two conical Adena mounds, a small mound with Fort Ancient burials, and much of a large Fort Ancient village laid over a smaller Adena occupation on the plateau south of the serpent; Hopewell pipes, points and an earspool and Adena gorgets are also displayed from the site. Salvage digs from 1988 to 1994 and in 2011 found that parts of both the Adena and Fort Ancient habitation areas survive, and a buried soil north of the large conical mound, excavated in 2011, yielded hickory charcoal dated to 900 +/- 25 radiocarbon years before present. Archaeologist Brad Lepper and colleagues read the mound as a creation story of the Great Serpent (Lord of the Beneath World) and First Woman best preserved among the Dhegiha Siouan tribes, while noting the story may once have been widely shared; the Shawnee have a tradition of a female creator and still have a Snake Clan in their traditional community. For the 2021 summer solstice the Shawnee Tribe returned to reconnect with a place sacred to their ancestors, and a sign at the site produced with the tribe quotes Chief Ben Barnes. No treaty cession specific to this parcel was found in published sources.

Later Indigenous use of the valley is recorded too. Putnam was shown the sites by a Mr. Hewes, whose grandfather had settled there, that a small band of Indians lived on the bottomland near the forks as late as 1800, and Putnam saw groups of their stone-lined graves on the surrounding hilltops. In 2017 the Ohio History Connection ended a popular winter-solstice luminaria at the effigy after consulting several American Indian tribes and deciding it was inappropriate.

• Great Serpent effigy: mound, Bluff above Ohio Brush Creek, Bratton Township, Disputed: c. 300 B.C. (Adena) or c. A.D. 1070 (Fort Ancient), possibly built early and repaired later
• Two Adena conical burial mounds: burial, Plateau south of the serpent, one near the parking lot, Early Woodland, 800 B.C.-A.D. 100
• Fort Ancient burial mound: burial, Near the serpent, A.D. 1000-1650
• Fort Ancient village over an earlier Adena occupation: village, Plateau south of the serpent, Early Woodland and Late Precontact
• Late Precontact buried soil north of the large conical mound: other, excavated by ASC Group in 2011, hickory charcoal dated 900 +/- 25 BP
• Historic-era Indian graves and camp near the forks of Brush Creek: burial, hilltops and bottomland around the serpent cliff, about 1800

Stories

Who built it, and when: a fight carried on in radiocarbon

Through the 20th century archaeologists disputed whether people of the Adena or the Fort Ancient culture built the serpent. Robert V. Fletcher and Terry L. Cameron, working with the Ohio Historical Society's Bradley T. Lepper, reopened a trench Frederic Ward Putnam had dug more than a century earlier and found charcoal in what they believed was an undisturbed part of the mound; two pieces dated to about A.D. 1070, placing the effigy in the Fort Ancient period, and the report appeared in 1996. In 2014 a new team's radiocarbon dates put construction at about 300 B.C. by Adena people, with a rebuilding or repair around A.D. 1100. Lepper answered that the 2014 team had dated organic sediment from soil cores rather than charcoal from an exposed profile, that such dates can run as much as 3,000 years too old, and that the Adena are not known to have built effigy mounds or used serpent imagery while the Fort Ancient people did. Lepper and colleagues concluded that the best available data point to Fort Ancient builders; the question is still argued. (source)

The case for Adena

The 2014 study grew out of the Serpent Mound Project, which William F. Romain began in 2010 to bring non-invasive and minimally invasive methods to the question: LiDAR, magnetic and resistivity surveys, ground-penetrating radar and coring. In April and September 2011 a tractor-mounted GeoProbe drove 18 cores along the effigy's spine, avoiding the oval and the tail; G. William Monaghan of Indiana University's Glenn A. Black Laboratory recovered nine samples with possible charcoal from five of them. The results, published in the Journal of Archaeological Science by Edward W. Herrmann and seven co-authors, put initial construction around 321 B.C., with a modeled range of 381 to 44 B.C. The authors read the 1991 Fort Ancient dates as coming from a later repair of an eroded section, and Romain and colleagues later pointed to a magnetic anomaly Jarrod Burks had found at the neck, which they took for an 'erased' coil, as evidence that the effigy had been altered at least once. (source)

The case for Fort Ancient

Lepper's replies ran in the Midcontinental Journal of Archaeology, the Cambridge Archaeological Journal and the Journal of Ohio Archaeology from 2018 to 2020. The 2014 dates, he wrote, were on soil humates, not charcoal, and Putnam had seen the builders strip the dark topsoil before laying the effigy, so old carbon in the truncated soil could long predate the mound. He cited a 2019 Danish study in which charcoal from soil cores came out 550 to 700 years older than a tree-ring date for one mound and about 3,000 years older than pyre charcoal in another, and noted that Herrmann's team had itself conceded the mound 'could have been constructed any time after 300 BC.' When Civilian Conservation Corps-era stone steps over the tail were removed in 2017, oak charcoal from the exposed strata dated to 1263 +/- 22 and 1300 +/- 30 BP, which Lepper called not inconsistent with a Fort Ancient age but definitely inconsistent with an Adena one. He suggested the old Adena attribution rested on Putnam's low opinion of the later villagers, and quoted the archaeologist James Griffin, who wrote that he 'simply couldn't abide' a late age for the serpent. (source)

The serpent in Picture Cave

Lepper and colleagues also argue from imagery. A panel of Mississippian pictographs in Picture Cave, Missouri, shows three motifs that match the effigy's three parts: the Great Serpent, an oval read as its open mouth, and a figure read as First Woman, 'mother of all living things' in Dhegiha Siouan tradition, who corresponds to the wishbone-shaped mound. That pictograph returned an AMS date of 950 +/- 100 BP, virtually identical to the 1991 Serpent Mound dates. In a 2020 paper Lepper suggested the effigy was built during severe droughts in the Mississippi valley that drove Mississippian refugees into the Ohio valley, by those refugees or by a Fort Ancient community they influenced, to call on the Great Serpent, Lord of the Beneath World, to keep conditions favorable. (source)

Sun, Moon or neither

The head and oval line up with the summer-solstice sunset. The body's coils are another matter. Some researchers align the three main curves with the solstice and equinox sunrises; others align the same curves with key moonrises in the 18.6-year lunar cycle. Ben Barnes and Brad Lepper wrote in 2021 that the sight lines are so short that there is 'a lot of wiggle room,' and 'They can't both be right.' They noted that two Late Precontact stone serpent effigies in the valley below Fort Ancient are also sun-aligned. The 2022 Hopewell World Heritage nomination takes the same skeptical view, saying the short sight lines and the lack of clear linearity render uncertain any judgment of the builders' intentions, and gives that, the effigy's likely date around 1100 CE and its builders' life as village-dwelling maize farmers as reasons it is not comparable to the Hopewell series.

Saved by Boston subscriptions

When Frederic Ward Putnam first saw the serpent in September 1883 it sat on John Lovett's farm, cleared after a windstorm around 1860 and plowed. Back in 1885 he judged its destruction inevitable, got Lovett to leave it alone for a year and took an option on the land. In Boston, Alice C. Fletcher took up the cause, and with help from historian Francis Parkman and Harvard's Martin Brimmer nearly $6,000 was raised, much of it from Boston women. The Peabody Museum's trustees took title, Putnam spent summers excavating and rebuilding the effigy, and Ohio passed what Putnam called the first American law protecting archaeological remains. After the distant museum struggled to care for it, Harvard deeded the park to the Ohio society in 1900 on condition it stay a free public park forever. (source)

Putnam's own account

Putnam told the story himself in The Century in April 1890. He had set out from Hillsborough with four fellow archaeologists, forded Brush Creek, scrambled up through briers and, reclining on one of the serpent's folds at sunset, resolved that 'the unknown must become known.' That evening he arranged with Lovett to have the brush cleared. Fletcher made her appeal to Boston women she met at Newport; he wrote that by 'June, 1886' he had nearly $6,000 and bought about sixty acres (his own letter of June 4, 1887 and the museum's reports put the money and the purchase in June 1887), then lived in tents for three seasons while digging and laying out the park. The Ohio law he praised, passed March 27, 1888, exempted such prehistoric parks from taxation and set fines of up to $50 or 60 days in jail for damaging them. Over three thousand people had visited in the previous summer, reaching it by rail to Peebles or Hillsborough and a drive of seven or eighteen miles. He also reached for Old World parallels, comparing the serpent with a serpent mound at Loch Nell in Scotland, much as Squier and Davis had compared it with the serpent temples of England. (source)

Egg, eye, frog, or First Woman

Squier and Davis saw the oval at the serpent's open jaws as an egg clutched in the serpent's jaws. In 1885 John MacLean mapped a wishbone-shaped mound at the oval's edge and called it a frog. Putnam left that feature off his published map, though it appears in his field notes, and Willoughby put it back on his 1919 map. Lepper and colleagues now read the whole as one scene from a creation story told among the Dhegiha Siouan tribes: the Great Serpent, Lord of the Beneath World, with First Woman as the wishbone mound. The head points toward the summer solstice sunset: Fletcher and Cameron measured the alignment's azimuth in 1988 at 300 degrees 5 minutes. (source)

The measurements of the oval have never agreed. Squier and Davis gave it as 160 by 80 feet, with a small pile of burned stones at its center that a treasure hunter had already thrown down; Putnam measured it at 120 by 60 feet, with banks about four feet high.

A mound on a crater

The bluff the serpent lies on is part of one of the oddest pieces of ground in Ohio. Around it, rock layers that normally lie deep underground are pushed up at the surface and ringed by down-dropped younger rock. Nineteenth-century geologists called it a sunken mountain; later ones blamed a hidden volcanic blast. Shatter cones and rocks normally found only deep underground eventually showed that an asteroid or comet struck here between 252 and 330 million years ago. (source)

Pilgrims, crystals and 'light warriors'

On August 16-17, 1987, about 3,000 people came for the Harmonic Convergence, a New Age event whose organizers had predicted as many as 12,000. Participants linked hands around the mound, and a tree near the serpent's head served as a makeshift altar with flowers and crystals under it; the crowd was reported well behaved. In September 2012 a group calling itself Team Light posted a 37-minute video of members running along and jumping on the serpent and describing resin-and-quartz 'orgone' devices they used to 'reactivate' it. Ohio History Connection staff later recovered three of the devices, one embedded in the top of the mound at the head. Archaeologists Robert Cook and Brad Lepper describe the episode as vandalism and treat such claims as modern forms of the old Moundbuilder Myth, which denied that American Indians built the earthworks. (source)

Luminaria, giants and the Friends of Serpent Mound

Cook and Lepper's 2025 paper also traces a local group, the Friends of Serpent Mound, founded in 2004 out of a county visitors bureau committee, partly prompted by a reported crop circle in a field across from the mound in 2003. Around 2005 the group began a winter-solstice 'Lighting of the Serpent,' setting more than a thousand luminary bags around the effigy, until the Ohio History Connection ended it in 2017 after consulting tribes; a newspaper columnist called that a 'religious test' and urged readers to lobby legislators. A co-founder of the group has claimed that the man Putnam found under the large conical mound stood at least 8 feet 9 inches. Asked by Lepper, Harvard's Peabody Museum measured the man's thighbones at 465 and 459 millimeters, which put his height at about 170 centimeters, 5 feet 7 inches, close to the Adena average; Putnam had written 'nearly six feet.' (source)

Who runs it

Harvard's 1900 deed passed the park to the Ohio State Archaeological and Historical Society, now the Ohio History Connection. When state funding was cut sharply in the 2009 financial crisis, the society handed day-to-day operation of many sites to local partners and chose the Arc of Appalachia to run Serpent Mound, a choice the Friends group criticized for the next decade. In 2026 the society's site page describes Serpent Mound as managed by the Ohio History Connection, open Tuesday through Sunday with a final entry at 4 p.m., at 3850 State Route 73 near Peebles. Drones are prohibited, access outside open hours is not permitted, and archaeologist Bill Kennedy leads a 90-minute walking tour from the museum on the second and fourth Friday of each month.

Timeline

• c. 300 B.C.: Construction date proposed by the 2014 Herrmann team from charcoal in cores along the effigy's spine (modeled range 381-44 B.C., median 321 B.C.), which would make the builders Adena people. (source)
• c. 1070: Construction date proposed by the Fletcher team from two wood charcoal samples that both dated to about A.D. 1070, which would make the builders Fort Ancient people. (source)
• 1845-1846: Ephraim G. Squier and Edwin H. Davis clear enough brush to survey the overgrown serpent at the 'Three Forks' of Brush Creek (Randall gives 1845 in one passage and 'about the year 1846' in another). (source)
• 1848: Squier and Davis publish the first description and map in Ancient Monuments of the Mississippi Valley, the first publication of the Smithsonian Institution. (source)
• c. 1859-1860: Thirteen or fourteen years after the Squier and Davis visit, a windstorm tears up the trees on the serpent hill; the land is then cleared and the mound damaged by plowing. (source)
• 1883: Frederic Ward Putnam of Harvard's Peabody Museum first visits the mound with four fellow archaeologists and finds it neglected; the land belongs to Mr. Lovett. (source)
• 1885: John MacLean publishes a map showing a wishbone-shaped mound beside the oval, which he interprets as a separate frog effigy. (source)
• 1885: On a second visit Putnam judges destruction inevitable, gets Lovett to agree not to disturb the mound for a year, and takes an option on some 65 or 70 acres. (source)
• 1887: On May 30 a Lovett writes to the Hillsboro News-Herald that an eastern buyer has taken about 58 acres and means to 'throw up the mound to its original height'; on June 4 Putnam writes that he will spend the autumn 'restoring the Serpent mound where it has been injured'; the Society's Quarterly prints the letter under the heading 'The Serpent Mound Saved'. (source) (source)
• 1887: In June, with nearly $6,000 raised largely by Boston women since the winter of 1886-87, Harvard's Peabody Museum buys about sixty acres of the Lovett farm, making Serpent Mound Park the first privately funded archaeological preserve in the nation. (source) (source)
• 1887-1889: Putnam spends parts of three successive seasons from 1887 at the park: eight weeks of the first restoring the oval and serpent and fencing them, then excavating the serpent, two Adena mounds, a Fort Ancient burial mound and village, and laying out the park. (source) (source)
• 1888: On March 27 Ohio passes the law exempting prehistoric parks from taxation and fining anyone who damages them, which Putnam called the first such law in the country. (source)
• 1890: Putnam publishes 'The Serpent Mound of Ohio' in The Century Magazine's April issue. (source)
• 1900: Harvard's governing board votes in May to give the park to the Ohio State Archaeological and Historical Society; the deed is acknowledged October 8 and recorded at West Union on November 22, on condition it be kept as a free public park forever. (source) (source) (source)
• 1901: Cincinnati surveyor Clinton Cowen maps the whole park, adding fanciful scales to the serpent. (source)
• 1902: On January 9 a Vermont granite tablet recording the mound's discovery, rescue and transfer is set on the conical mound about 300 feet south of the serpent's tail. (source)
• 1902: On May 30, after repairs by the park's custodian, Daniel Wallace, the Society's secretary finds the effigy 'thoroughly restored to serpentine perfection'. (source)
• 1919: Charles Willoughby publishes a map counting the wishbone-shaped mound and the neck projections as parts of the effigy, and reports that Putnam's restoration raised the banks 'in some places probably at least a foot' and narrowed them, while 'the original form of the effigy was not materially altered'. (source) (source)
• 1933-1935: Depression work-relief crews (the Civil Works Administration, then a federal relief camp) work in the park, and the Society's curator reports supervising 'restoration and maintenance of earthworks' there; Rory Krupp, writing in the Journal of Ohio Archaeology in 2020, argues from the Society's archives that the serpent was restored again in 1934-35, though how much was added was not recorded. (source) (source)
• 1987: About 3,000 people gather at the mound on August 16-17 for the Harmonic Convergence. (source)
• 1988-1994: The Ohio History Connection runs salvage excavations along a waterline to the museum and finds Fort Ancient and Adena habitation areas largely preserved. (source)
• 1991: Robert Fletcher, Terry Cameron, Bradley Lepper and Dee Anne Wymer reopen one of Putnam's back-filled trenches and take two charcoal samples dated to 920 +/- 70 radiocarbon years before present (published 1996). (source)
• 2004: The Friends of Serpent Mound is founded; its winter-solstice luminaria begins around 2005. (source)
• 2008: The U.S. Department of the Interior places Serpent Mound and eight other Ohio earthworks on the Tentative List for UNESCO World Heritage nomination; Serpent Mound's entry is dated January 30. (source) (source)
• 2009: After state funding cuts, the Ohio History Connection chooses the Arc of Appalachia to operate the site. (source)
• 2011: William Romain's Serpent Mound Project takes 18 GeoProbe cores along the effigy in April and September. (source)
• 2011-2012: Archaeologist Jarrod Burks's magnetic survey finds a coil-sized arc on the east side of the neck, trenched in June 2012; he reads it as a coil erased in antiquity or never finished, and it cannot be dated. (source) (source)
• 2012: A group calling itself 'Team Light' posts a video on September 10 of members running on the effigy and burying resin-and-quartz 'orgonite' devices in and near it. (source)
• 2014: Herrmann and colleagues publish the Adena construction dates in the Journal of Archaeological Science. (source)
• 2015: Over the Fourth of July weekend a 19-year-old drives a pickup over an Adena burial mound near the effigy; he confesses, and damages are put at more than $3,000. (source)
• 2017: CCC-era stone steps over the tail are removed, yielding new charcoal dates; the Ohio History Connection ends the solstice luminaria after consulting tribes. (source)
• 2021: Shawnee Tribe Chief Ben Barnes and Brad Lepper publish a joint history of the mound as the Shawnee return for the summer solstice. (source)
• 2023: The Hopewell Ceremonial Earthworks are inscribed on the World Heritage List without Serpent Mound, which remains on the Tentative List as a separate site. (source) (source)

Sources

• ohiohistory.org: serpent mound
• ohiohistory.org: ohios serpent mound an american indian story written in the earth
• ohiohistory.org: serpent mound park in 1901
• archive.org: serpentmoundadam00randuoft djvu.txt
• archive.org: Putnam, 'The Serpent Mound of Ohio,' The Century, April 1890
• archive.org: Squier and Davis, Ancient Monuments of the Mississippi Valley (1848)
• kb.osu.edu: content
• kb.osu.edu: content
• ohiodnr.gov: serpent mound impact
• archive.archaeology.org: serpentmound
• ancientearthworksproject.org: new radiocarbon dates suggest serpent mound is more than 2000 years old
• ohioarchaeology.org: Cook and Lepper, Uncoiling Serpent Mound's 'Slithery Vibe' (Journal of Ohio Archaeology, 2025)
• ohioarchaeology.org: Lepper, The Mississippian Iconography of Serpent Mound (Journal of Ohio Archaeology, 2020)
• ohioarchaeology.org: Lepper, Why Radiocarbon Dates on Bulk Sediment from Serpent Mound Are Problematic (2020)
• whc.unesco.org: Serpent Mound, U.S. Tentative List (2008)
• whc.unesco.org: Hopewell Ceremonial Earthworks, World Heritage nomination (2022)
• archaeology.org: Accused Vandal Could Be Assigned Research Paper
• commons.wikimedia.org: Category:Serpent Mound
• npgallery.nps.gov: 66000602 text
• archive.org: Reports of the Peabody Museum, 20th-24th (1886-1890)
• archive.org: Ohio Archaeological and Historical Quarterly, vol. 1 (1887-88)
• archive.org: Willoughby, 'The Serpent Mound of Adams County, Ohio', American Anthropologist 21 (1919)
• loc.gov: Hillsboro News-Herald, June 9, 1887
• archive.org: Ohio Archaeological and Historical Quarterly, vol. 9 (1901)
• archive.org: Ohio Archaeological and Historical Quarterly, vol. 10 (1902)
• archive.org: Ohio Archaeological and Historical Quarterly, vol. 11 (1902)
• archive.org: Ohio Archaeological and Historical Quarterly, vol. 43 (1934)
• ohioarchaeology.org: Krupp, 'New Deal, New Serpent' (Journal of Ohio Archaeology, 2020)
• archprospection.org: Burks, 'Ohio's Great Serpent Mound Surveyed', ISAP News 32 (2012)