In August 1817, hundreds of people in and around Gloucester, Massachusetts, reported a huge sea serpent swimming in their harbor. It was described as dark, jointed or humped like a string of barrels, sixty feet long or more, with a head like a turtle’s or a horse’s. The sightings were taken so seriously that the Linnaean Society of New England, led by a federal judge and a Harvard physician, collected sworn testimony from witnesses, and then made one of the most famous mistakes in American natural history.[1][2][3]
| Location | Gloucester Harbor and Cape Ann, Massachusetts; later Nahant |
|---|---|
| Main sightings | August 1817, continuing into 1818 and 1819 |
| Reported description | Dark, 60–100 ft long, a row of humps “like a string of buoys,” head like a turtle’s or horse’s, sometimes with a spike |
| Investigators | Linnaean Society of New England committee: Judge John Davis, Dr. Jacob Bigelow, Francis C. Gray |
| Famous mistake | Scoliophis atlanticus, a “baby serpent” that was really a deformed black snake |
| Earliest Cape Ann report | John Josselyn, 1638 |
| Leading explanations | Lines of tuna, whales, porpoises or seals; boat wakes; swordfish; social contagion |
An old tradition
Cape Ann had sea serpent stories long before 1817. The English traveler John Josselyn, in his account of voyages to New England, recorded being told of a sea serpent seen at Cape Ann during his first visit in 1638, showing that the idea of a serpent off that coast was already circulating among colonists.[1][4]
August 1817
The great sightings began in early August 1817, with reports from about 10 August. On 18 August the Boston Daily Advertiser reported a “prodigious snake” in Gloucester Harbor, seen by hundreds of people over several days.[3][5]
Witnesses included fishermen, ship captains, merchants and ordinary townspeople, many watching from shore. Their descriptions varied but shared common features:[1][5][6]
- a dark body moving in vertical undulations, described as a line of humps or joints, sometimes compared to “a string of casks” or a rope lined with buoys;
- a length usually estimated at 60 to 100 feet; Solomon Allen III put it at 80 to 90 feet;
- a head about the size of a hat’s crown, according to James Mansfield, likened to a turtle’s or a horse’s, sometimes with a spike or “sting” about a foot long;
- great speed, and the ability to turn sharply and sink straight down.
Several people tried to kill it. Muskets were fired at close range with no visible effect, and a cash reward was offered for its capture. General David Humphreys, a former aide-de-camp to George Washington, traveled to Gloucester to interview witnesses and estimated that some two hundred people had seen the creature at once.[5][6]
The Linnaean Society investigates
On 18 August 1817, the Linnaean Society of New England, a young natural history society in Boston, formed a committee to collect evidence. Its members were John Davis, a US District Court judge and the society’s president; Jacob Bigelow, a physician and botanist who later taught at Harvard; and Francis C. Gray. They arranged for sworn statements to be collected from witnesses, who were asked the same set of questions about distance, size, color, shape and motion so their answers could be compared.[2][3]
The committee’s report, published in Boston in 1817 as Report of a Committee of the Linnaean Society of New England, relative to a large marine animal, supposed to be a serpent, seen near Cape Ann, printed the depositions in full. It is one of the earliest attempts in America to investigate a reported unknown animal through systematic eyewitness testimony.[2][7]
The “baby serpent”
On 27 September 1817, a Gloucester resident named Gorham Norwood killed an unusual snake, about three feet long, in a field near the shore. Its body was strangely humped along the back. The committee, which believed the great serpent had come into the harbor to breed, concluded that this was one of its young.[3][6]
In its report the society declared a new genus and species, Scoliophis atlanticus, the “Atlantic humped snake,” and included a fold-out plate of the specimen. Judge Davis admitted privately that it was “rather bold” to propose a new genus, but felt the animal’s features required it.[3]
It did not last. The French naturalist Charles Alexandre Lesueur examined the specimen and showed that it was a common black snake (Coluber constrictor) with a deformed, diseased spine. The Boston Society of Natural History formally reviewed the episode in its Proceedings in the 1860s. The embarrassing “baby” did a great deal to make scientists wary of sea serpents for the rest of the century.[3][6][8]
Ridicule, satire and Nahant
The sightings and the Linnaean report drew ridicule from outside New England. In 1819 the Charleston playwright William Crafts staged The Sea Serpent; or, Gloucester Hoax, which suggested the whole affair was a stunt to promote the town.[1][5]
Yet sightings went on, including mass sightings off Nahant, near Boston, in 1819. Jacob Bigelow published “Documents and Remarks respecting the Sea Serpent” in the American Journal of Science in 1820, and reports continued sporadically through the nineteenth century and beyond.[1][5]
What did they see?
- Lines of fish or mammals. A line of tuna, porpoises or seals swimming one behind another can look like a single long, humped body. One nineteenth-century Gloucester captain who hunted the serpent concluded that it was a bluefin tuna whose wake created the humps, and the Boston Society of Natural History suggested a humpback whale feeding on fish.[3][4]
- Boat wakes. In 2024 Brian Dunning of Skeptoid noted that all the sightings he could locate were inside the harbor and suggested that intersecting boat wakes, which form regularly spaced crests, could produce a moving line of “humps.” He also suggested that the “sting” could be the bill of a swordfish, common off New England.[9]
- Narwhals. The investigator Joe Nickell proposed in 2019 that the “sting” pointed to a line of tusked narwhals, although narwhals do not normally live this far south.[1][9]
- Entangled or harpooned animals. Other researchers have suggested that whales towing fishing gear or overturned boats explain some sea serpent sightings of the period.[1]
- Social contagion. Once the serpent was in the newspapers, many people who had never been to sea came to the shore expecting to see it, and the excitement shaped what they reported.[9]
Today Gloucester celebrates its serpent: a sculpture of it was unveiled at the Cape Ann Museum in 2019.[1] For another sea serpent, see Cadborosaurus, and for a lake monster, Champ.
References
- “Gloucester sea serpent,” Wikipedia, citing J. P. O’Neill, The Great New England Sea Serpent (2003); W. Soini, Gloucester’s Sea Serpent (2010); C. M. Brown, American Quarterly 42 (1990); and others.
- Linnaean Society of New England, Report of a Committee of the Linnaean Society of New England, relative to a large marine animal, supposed to be a serpent, seen near Cape Ann, Massachusetts, in August 1817 (Boston: Cummings and Hilliard, 1817). Biodiversity Heritage Library.
- “‘It appeared so strange and wonderful…’,” Massachusetts Historical Society (October 2019).
- “The Great New England Sea Serpents,” New England Historical Society.
- “The Gloucester Sea Serpent,” Museum of Hoaxes.
- Lucas Reilly, “Revisiting the Mystery of the Great New England Sea Serpent of 1817,” Mental Floss (2 October 2018).
- Chandos Michael Brown, “A Natural History of the Gloucester Sea Serpent: Knowledge, Power, and the Culture of Science in Antebellum America,” American Quarterly 42, no. 3 (1990): 402–436.
- Grace Costantino, “Five ‘Real’ Sea Monsters Brought to Life by Early Naturalists,” Smithsonian (27 October 2014).
- Brian Dunning, “Hunting the Gloucester Sea Serpent,” Skeptoid episode 963 (19 November 2024).
Correction note (October 2026): This entry was rewritten from historical sources, replacing an earlier general description. The illustration above is an artistic impression.