In 1838, John Estaugh Hopkins was digging in a marl pit (on a small tributary of the Cooper River in Haddonfield, New Jersey, and part of the Campanian-age Woodbury Formation) when he uncovered large bones, putting them on display at his home, also in Haddonfield. In 1858, these bones sparked the interest of a visitor, William Parker Foulke. The skeleton was dug out from the marl pit in 1858 by Foulke. The excavation site, known as the "Hadrosaurus foulkii" Leidy site, is now a National Historic Landmark. Foulke contacted paleontologist Joseph Leidy, and together they recovered 8 teeth from the maxillar and dentary areas, dental battery fragments, left maxilla fragments, 3 partial dorsal vertebrae, 13 caudal centra including an almost complete middle caudal vertebra and other fragments, partial right coracoid, left humerus, left radius, left ulna, left ilium, right ischium, right partial pubis, the left hindlimb composed by the femur, tibia, fibula with metatarsals II and IV and the first pedal phalanx from the third digit. Foulke and Leidy studied the fossils together, and in 1858, Leidy formally described and named "Hadrosaurus foulkii" in honor of his collaborator. While originally a portmanteau of Haddonfield, the location of its discovery with the accepted suffix for dinosaurs -saurus, the name "Hadrosaurus" was scientifically justified as deriving from the Greek , , meaning "bulky" or "large", and , , meaning "lizard". The name was an additional play on words by Leidy since it translates from Greek as "Foulke’s big lizard".