In 1835 Edward Hitchcock was Professor of Geology at Amherst College in Massachussetts. In that year he was shown a slab of rock from the Connecticut valley which contained some footprints. In 1836 he published a paper describing the slab, and continued to collect footprints and write articles for another 20 years.
Nearly all the prints that Hitchcock colected and studied were made by Triassic dinosaurs. At this time, however, all dinosaurs were thought to be quadrupedal and as these prints were bipedal they were thought to have been made by large birds.
Ironically in the year that Hitchcocks most substantial work was published (1858), Joseph Leidy was discovering sound evidence in New Jersey for the existence of bipedal dinosaurs.