In 1818, Samuel L. Mitchill briefly detailed a fossil vertebral column with teeth found in North Carolina. It was believed to have been a sea serpent or giant shark and it was lost in a museum fire in 1866. Its true identity is difficult to ascertain with the sparse information and absence of illustrations. This specimen, dubbed ‘Mitchill’s monster’, is reevaluated here with modern geological and paleontological knowledge. It probably came from the marine, Mio-Pliocene Eastover or Yorktown Formations. It was most likely baleen whale vertebrae with associated teeth of the megatooth shark Otodus megalodon, yet it is also not impossible that both the vertebrae and teeth were O. megalodon. Regardless of which hypothesis is correct, the monster would have been a major discovery.