The scientific recognition of dinosaurs in North America emerged during the mid-19th century. Although the term “dinosaur” was coined in England in 1842, it was unclear if these ancient reptiles had roamed the American continent. Paleontology in the United States initially focused on large, extinct mammals, but definitive proof of its dinosaurian past was slow to arrive. Subsequent discoveries confirmed the presence of these reptiles and propelled American science to the forefront of the field, leading from fragmented finds in the East to massive bone beds in the West.
The First Recognized American Dinosaur
The first scientifically recognized dinosaur remains in North America were highly fragmented, consisting primarily of isolated teeth and bone pieces. In 1856, paleontologist Joseph Leidy described teeth collected by Ferdinand Vandiveer Hayden from the Judith River region of the Nebraska Territory, assigning them to the genera Trachodon and Deinodon. These initial finds, while significant, did not provide enough material for a complete reconstruction.
The turning point came in 1858, in Haddonfield, New Jersey, when amateur naturalist William Parker Foulke investigated a marl pit. Workers had previously unearthed several large bones, and Foulke organized an excavation that recovered a partial, but much more complete, skeleton of a large herbivore.
Leidy, a professor of anatomy in Philadelphia, examined the fossils. He determined the specimen belonged to a dinosaur, naming it Hadrosaurus foulkii (Foulke’s bulky lizard). The discovery was important because the limb proportions indicated the animal was bipedal, a concept that challenged existing ideas. The Hadrosaurus find provided the first substantial anatomical proof of a North American dinosaur.
Unearthing the Western Fossil Beds
Following the initial finds in the East, dinosaur discovery shifted westward, driven by geological exploration and the expansion of the United States. Federal and private surveys pushed into the territories, exposing previously inaccessible rock layers. Infrastructure projects, such as the transcontinental railroad, also helped reveal massive fossil deposits.
The geological context of the West proved far richer than the coastal plains of New Jersey. The Late Jurassic Morrison Formation, a sedimentary rock unit stretching from Montana to New Mexico, became a major source of fossils. This formation, dating to 148–155 million years ago, contained the remains of numerous dinosaur species deposited in ancient river channels and floodplains.
Large-scale discoveries within the Morrison Formation began in the late 1870s in areas like Como Bluff, Wyoming, and near Morrison, Colorado. This shift provided an abundance of material, including nearly complete skeletons, that dwarfed the earlier Eastern finds.
The Age of Competitive Discovery
The sudden wealth of fossils in the West fueled a period of intense competition known as the Bone Wars, which spanned the 1870s through the 1890s. The rivalry pitted two prominent American paleontologists: Othniel Charles Marsh of Yale University and Edward Drinker Cope of the Academy of Natural Sciences of Philadelphia. These two men funded their own expeditions, dispatching teams of bone hunters to actively compete for the richest dig sites.
The competition was fierce, marked by attempts to sabotage rivals, bribe workers, and rush discoveries into publication. Marsh and Cope used underhanded tactics, including destroying fossils to prevent them from falling into the other’s hands. This relentless drive, despite its unethical nature, led to an unprecedented number of discoveries.
The era of the Bone Wars led to the identification and naming of many of the most iconic American dinosaurs. Among the new species described were the long-necked sauropods Apatosaurus and Diplodocus, Stegosaurus, and Triceratops. By the end of the rivalry, the two men had collectively discovered and described over 140 new species of dinosaurs, fundamentally shaping the public understanding of prehistoric life and establishing American paleontology as a global force.