How Thomas Jefferson's Obsession With Mastodons Partly Fueled the Lewis and Clark Expedition

By the 1800s, American mastodons—prehistoric relatives of the elephant—had been extinct for roughly 10,000 years. Thomas Jefferson didn’t know that, though. The Founding Father dreamed of finding a living, breathing mastodon in America, and this lofty goal ended up being a motivating force throughout much of his life. Even during the Revolutionary War, and even when he ran for the highest office in the land, he had mastodons on the mind. Jefferson was convinced that the hairy beasts still roamed the continent, probably somewhere on the uncharted western frontier, and he was determined to find them—or, at the very least, enlist a couple of intrepid explorers by the names of Meriwether Lewis and William Clark to do the hunting on his behalf.

The Corps of Discovery departed from St. Louis on May 14, 1804 and headed into the great unknown of the Louisiana Purchase in search of an all-water route to the Pacific. The adventurers made many discoveries on the two-and-a-half-year round trip—mapping the geography of the region and logging hundreds of species of flora and fauna unknown to science—but the directive to look for mastodons is a little-known footnote to their famous expedition.

At the start of their trip, Jefferson instructed Lewis and Clark to be on the lookout for “the remains and accounts of any [animal] which may be deemed rare or extinct.” Although he didn’t mention mastodons specifically—at least not in any of the written correspondence on record—the two explorers were all too familiar with Jefferson’s mammoth ambition. “Surely Jefferson still had the M-word in mind, and surely Lewis knew it,” author Robert A. Saindon writes in Explorations Into the World of Lewis and Clark, Volume 2.

Jefferson had long been interested in paleontology, but his mastodon obsession was fueled by a longstanding beef he had with a French naturalist who thought America’s animals and people were puny. Jefferson’s bone-collecting hobby quickly evolved into a mission to assert America’s dominance in the Western world and prove that it was "a land full of big and beautiful things," as journalist Jon Mooallem put it in his book, Wild Ones. Indeed, there are worse ways to become a political and cultural heavyweight than to prove your country is home to a 12,000-pound monster.

A Rivalry Forms

For much of his adult life, Jefferson was an avid collector of fossils and bones. At various points in time, he owned a bison fossil, elk and moose antlers, giant ground sloth fossils, and naturally, a number of mastodon bones.

Though his original interest may have been purely academic, Jefferson's exposure to the writings of French naturalist Georges-Louis Leclerc, Comte de Buffon fanned the flames of his obsession. Buffon’s “Theory of American Degeneracy,” published in the 1760s, postulated that the people and animals of America were small and weak because the climate (he assumed, without much evidence) was too cold and wet to encourage growth.

Jefferson was furious. He formulated a rebuttal, which partly drew attention to the inconsistencies in Buffon's beliefs about the mastodon. Buffon suggested that the American mastodon was a combination of elephant and hippopotamus bones, but because Jefferson had inspected the bones, he knew that the measurements didn't match those of previously known species. Instead, Jefferson argued that the bones belonged to a different animal entirely. (Although they’re distinct species, woolly mammoths and mastodons were lumped into the same category at the time, and were called one of two names: mammoths or the American incognitum.)

“The skeleton of the mammoth … bespeaks an animal of five or six times the cubic volume of the elephant,” Jefferson wrote. He later scaled back his argument a bit, adding, “But to whatever animal we ascribe these remains, it is certain such a one has existed in America, and that it has been the largest of all terrestrial beings.”

He didn’t just believe that mastodons had existed at one point in time, though—he believed they were still out there somewhere. It wasn’t unusual for thinkers and scientists of Jefferson's era to assume that bones were evidence of a still-living species. After all, dinosaurs had not yet been discovered (though their bones had been found, no one would call them dinosaurs until the early 19th century), and the concept of extinction wasn’t widely accepted or understood. Dominant religious beliefs also reinforced the idea that God’s creations couldn't be destroyed.

For his part, Jefferson believed that animals fell into a natural order, and that removing a link in “nature’s chain” would throw the whole system into disarray. Taking the tone of a philosopher, he once questioned, “It may be asked, why I insert the Mammoth, as if it still existed? I ask in return, why I should omit it, as if it did not exist?”

This position may have been partly fueled by wishful thinking. Jefferson believed that tracking down a living mastodon would be the most satisfying way to stick it to Buffon and say, “I told you so.” (In the meantime, though, he had to settle for a dead moose, which he sent overseas to the Frenchman’s doorstep in Paris to prove that large animals did, in fact, exist in America.)

The Hunt Continues

In late 1781, Jefferson wrote to his buddy George Rogers Clark in the Ohio valley and asked him to fetch some mastodon teeth from a nearby "mastodon boneyard" in northern Kentucky called Big Bone Lick. “Were it possible to get a tooth of each kind, that is to say a foretooth, grinder, &c, it would particularly oblige me,” Jefferson wrote. Clark politely explained that the possibility of Native American attacks made this task impossible, but he was able to procure a thighbone, jaw bone, grinder, and tusk from travelers who had managed to visit the frontier.

However, Jefferson didn’t receive Clark's reply until six months later in August 1782 (because of, you know, the Revolutionary War). Although the war technically didn't end until the following year, peace talks between the two sides were nearing a conclusion, and everybody knew it. With an end to the conflict in sight, Jefferson doubled down on his request for mastodon bones. He wrote to Clark, “A specimen of each of the several species of bones now to be found is to me the most desireable object in Natural History, and there is no expence of package or of safe transportation which I will not gladly reimburse to procure them safely.”

Later, while serving as America’s first Secretary of State, Jefferson supported a proposed Western exploration that would have preceded the Lewis and Clark expedition. Before the expedition was called off, Jefferson had instructed the would-be explorer, French botanist André Michaux, to look for mastodons along the way. He wrote to Michaux in 1793, “Under the head of Animal history, that of the Mammoth is particularly recommended to your enquiries.”

Even when Jefferson turned his attention to national politics and ran for president against incumbent John Adams in 1800, he was still thinking about mastodons. His preoccupations were so widely known that his opponents, the Federalists, called him a “mammoth infidel” in reference to his unusual hobby and supposed secular leanings. As an 1885 article in the Magazine of American History recalled, “When Congress was vainly trying to untangle the difficulties arising from the tie vote between Jefferson and [Aaron] Burr, when every politician at the capital was busy with schemes and counter-schemes, this man, whose political fate was balanced on a razor’s edge, was corresponding with [physician and professor] Dr. [Caspar] Wistar in regard to some bones of the mammoth which he had just procured from Shawangunk, Ulster County.”

Once president, Jefferson used his office to further the field of paleontology. Not long after he was elected, he loaned one of the Navy’s pumps to artist and naturalist Charles Willson Peale, who wanted to extract a pile of freshly unearthed mastodon bones from a water-filled pit. It ultimately became the first fossilized skeleton to ever be assembled in America.

Of course, there is also evidence that Jefferson silently hoped Lewis and Clark would stumble upon a living mastodon during their expedition, which formally kicked off in 1804 and ended in 1806. That, as we now know, was impossible. After their return, Jefferson sent William Clark on a second assignment to collect artifacts from Big Bone Lick. He sent three big boxes of bones back to Jefferson, who got to work unloading and studying them in the East Room of the White House—the same room where John and Abigail Adams once hung their laundry.

Still, something wasn’t quite right, and Jefferson may have known it even then. By 1809, the animal in question had been identified and given the name mastodon, and Jefferson started to reverse some of his previously held opinions. In a letter to William Clark, he conceded that the mastodon was not a carnivore, as he once believed, but an herbivore. "Nature seems not to have provided other food sufficient for him," he wrote, "and the limb of a tree would be no more to him than a bough of cotton tree to a horse."

Accepting the Mastodon’s Fate

The fact that Lewis and Clark never spotted any giants roaming out West may have helped Jefferson accept the inevitable: Mastodons had gone extinct long ago. Waxing poetic in a letter to John Adams in 1823, Jefferson wrote, “Stars, well known, have disappeared, new ones have come into view, comets, in their incalculable courses, may run foul of suns and planets and require renovation under other laws; certain races of animals are become extinct; and, were there no restoring power, all existences might extinguish successively, one by one, until all should be reduced to a shapeless chaos.”

Although he was unsuccessful in his quest to find a living mastodon, Jefferson made other meaningful contributions to the field of paleontology. The fossils of another mysterious creature he believed to be a lion were later revealed to be that of a giant ground sloth. He named it Megalonyx (Greek for “great claw”), and in 1822, the extinct creature was renamed Megalonyx jeffersonii in Jefferson’s honor.

Nowadays, the ground sloth fossils—and several other items that formed the "cabinet of curiosities" Jefferson displayed at his Monticello estate—are part of The Academy of Natural Science collection at Drexel University. Considering that Jefferson is sometimes called "the founder of North American paleontology,” it would appear he got his revenge against Buffon after all.