"Christopher Anvil" is a pseudonym used by author Harry C. Crosby (1922-2009). Harry Crosby's first published short story was "Cinderella, Inc.", which appeared in the December 1952 issue of Imagination. By 1956, he had adopted the pseudonym and was being published in Astounding Magazine. His first published book was The Day the Machines Stopped (1964). He is best known for his Federation of Humanity series, which he referred to as the Colonization Series before they were published as collections. Most of his published works are short stories, and he has also produced four novels.