John Cassin (September 6, 1813 – January 10, 1869) was an American ornithologist. He is considered to be one of the giants of American ornithology, and was America's first taxonomist, describing 198 birds not previously mentioned by Alexander Wilson and John James Audubon. Cassin drew, printed and hand-colored many of the illustrations for the Pacific Railroad Surveys as the western regions of the United States were explored. He was named curator of the Philadelphia Academy of Natural Sciences in 1842, and after John T. Bowen's death, he took control of the Academy. His "Illustrations" was intended to be a 3-volume work, but financial considerations prevented more than one volume being published.