One of the often-repeated misconceptions about the Lewis and Clark expedition is that on their Voyage of Discovery they expected they might see dinosaurs or prehistoric creatures still living in the wild American West. This statement is not correct for several reasons. First and foremost, in 1804 dinosaur remains had not yet been discovered and identified as such anywhere in the world. Put another way, people in 1804, even Thomas Jefferson and the foremost scientists of the day, knew nothing about dinosaurs. The notions of prehistoric creatures and extinction were so new that President Jefferson and Meriwether Lewis cannot really be considered naive for thinking that mammoths or mastodons (which had been discovered) might still exist in the West. For Jefferson and Lewis, mammoths were not necessarily "prehistoric creatures." Dinosaurs, however, were another matter entirely. The term "dinosaur" wasn't even coined until 1842, and the idea of extinct reptilian lifeforms was quite radical even then, forty years after Lewis and Clark's expedition. Charles Darwin, natural selection, evolution, patterns of extinction, and the geological dating of fossil remains were all far in the future in 1804.
Notions about the age of the earth were changing near the turn of the 19th century, however, with the 1797 publication of the theories of James Hutton, a Scotsman who has been called "the Father of Geology." Hutton described an earth that was destroying and renewing itself in a never-ending cycle which showed "no vestige of a beginning, - no prospect of an end." Some scientists and philosophers were beginning to think that the earth might be anywhere from 100,000 years old up to several million years old, based on the amount of sedimentary rock they observed at different locations.
The other major notion of the early 19th century which made fossil finds difficult to reconcile was the concept of extinction. Why would God create a creature or a species and then let all of them die off? In 1804, it was thought by most Europeans and Americans that all species were saved by Noah on his Ark. The idea of extinction, then, seemed to go against what was written in the Bible. At the time of Lewis and Clark, the most extensive work on fossils had been conducted by the French scientist Georges Leopold Chrétien, Baron Cuvier (1773-1838). Cuvier began his work at the Jardin des Plantes in Paris, France's museum of natural history, in 1799. Cuvier initiated the science of "comparative anatomy," looking at the bones of animals and identifying the functions of each, comparing them with similar creatures. In 1804, Cuvier was just developing his notion that, from his study of fossil remains, some of God's creatures had in fact become extinct. In other words, at the time of Lewis and Clark, the search for fossil remains had just begun, and few people believed in the possibility of extinction.
Every story has a little grain of truth to it, however, and the story of Lewis and Clark looking "for dinosaurs" is no exception. By 1804, Thomas Jefferson, Charles Willson Peale, Caspar Wistar and other scientific Americans had excavated the skeletons of mammoths, which they called the "great incognitum," and "a large lion-like creature" Jefferson called Megalonyx (later identified as a giant ground sloth) in New Jersey and Virginia. They believed that these animals might still be living further to the West. Why? Because if no creatures ever created by God had become extinct, then every creature, even those for which fossilized remains were found, still existed somewhere on earth. Jefferson differed from most men of his time in that he believed that extinction might be possible, although the chance that mammoths still lived in the West was also very real to him. Jefferson wrote to the prominent French naturalist Bernard Germain Etienne de la Ville sue Illion, Comte de Lacépède (1756-1825) on February 24, 1803, about the upcoming expedition to be led by Meriwether Lewis. Jefferson told Lacépède that it was "not improbable that this voyage of discovery will procure us further information of the Mammoth, & of the Megatherium also. . . " The President described the Megalonyx, which was similar to a specimen found in France which Lacépède had found. Jefferson added that there were "symptoms of it's late and present existence. The route we are exploring will perhaps bring us further evidence of it. . ."
Jefferson had been interested in fossil remains for many years. In his tangle with the Comte de Buffon, which resulted in Notes on the State of Virginia, Jefferson not only proved that North America had larger living animals than Europe (with the example of the moose), but also claimed a fossil record of larger finds with the "great incognitum." As a result, Lewis and Clark were on the lookout for mammoths, sloths, or other creatures unknown thus far to science. In Jefferson's orders to the co-captains, they were to observe "the animals of the country generally, & especially those not known in the U.S. the remains and accounts of any which may [be] deemed rare or extinct." Lewis and Clark found no mammoths, but they did find many creatures previously unknown to science: the grizzly bear, prairie dog, pronghorn antelope, and mountain goat, along with many other species and subspecies of animals. Perhaps animals like the pronghorn were every bit as "otherworldly" to them as dinosaurs seem to us today.
Perhaps the most interesting sidelight on the expedition itself with reference to dinosaurs is that although Lewis and Clark were not looking for dinosaurs during their Voyage of Discovery, they nevertheless encountered them and described them for science! There are four instances where fossil evidence of prehistoric creatures was discussed in the journals of the Lewis and Clark expedition. The first was on September 28, 1803 in Cincinnati, Ohio.
The second instance of the discovery of fossil remains was on August 6, 1804, when then-Pvt. Patrick Gass found the "Petrified Jawbone of a fish or some other animal . . . in a cavern a few miles distance from the Missouri" (the expedition was encamped midway between present-day Omaha, Nebraska and Sioux City, Iowa at the time). Curiously, the August 6 find was not mentioned in the Journals of Lewis and Clark, or by Gass in his journal. It was only found in the descriptions of mineralogical specimens sent back to President Jefferson from Fort Mandan in 1805.
The third find occured on September 10, 1804, while the Corps was making its way up the Missouri River in the vicinity of present-day Geddes, South Dakota. On an island in the middle of the Missouri dubbed Cedar Island, William Clark found the fossil remains of the backbone, teeth and ribs of a plesiosaur, an ocean-dwelling creature of the Mesozoic Era. This fossil find was astonishing if only for its enormity - the backbone of the creature was 45 feet long! The bones were thought to be those of a large fish by Clark and the other journalists (Gass, Ordway and Whitehouse). Gass noted that some of the vertrbra were sent back to "Washington City" with the various specimens from Fort Mandan in the spring of 1805. The footnote in Gary Moulton's edition of the journals notes that "some of the vertebra apparently are now in the Smithsonian Institution."
On the return journey, July 25, 1806 near Pompey's Pillar in Montana, William Clark reported the fourth and final fossil find of the expedition relating to prehistoric creatures. Clark said that he "employed himself in getting pieces of the rib of a fish which was Semented within the face of the rock this rib is about 3 inchs in Secumpherance about the middle [the fallen rock is near the water - the face of the rock where the rib is is perpendr. - 4 is. langthwise, a little barb projects] it is 3 feet in length tho a part of the end appears to have been broken off I have Several peces of this rib the bone is neither decayed nor petrified but very rotten. the part which I could not get out may be Seen, it is about 6 or 7 Miles below Pompey's Tower in the face of the Lard. [larboard] Clift about 20 feet above the water."
Today we know that Clark's fossil find was in a rock strata from the Cretaceous Period (144-65 million years ago), the last of the three eras of the dinosaurs. It is in an area that was a terrestrial zone during the Cretaceous, thus ruling out Capt. Clark's guess that he had discovered "the rib of a fish." Having seen the carcass of a whale on the Pacific coast, Clark might be expected to jump to the conclusion that the giant ribcage he saw protruding from the rock was a large "fish" (dolphins and whales were not generally recognized as seagoing mammals in the early 19th century, and were often called fish). So what did Capt. Clark really find? The most common dinosaurs found in the rock strata Clark described, the Hell Creek Formation in Montana, are Hadrosaurs ("duck-billed dinosaurs"), Triceratops, Albertosaurus, and Tyrannosaurus Rex. In other words, although Lewis and Clark knew nothing of dinosaurs, and were not looking for dinosaurs on their Voyage of Discovery, they may have found a dinosaur.
Clark's dinosaur find, although not well chronicled in terms of exactly what he found, is commonly cited in books about paleontology as one of the earliest world-wide finds of dinosaur bones. In addition to all of their other finds, the Corps of Discovery paved the way for 19th century bone hunters and 20th century paleontologists in the American West.