Born in Pueblo, Colorado, John McDermott was a self-taught illustrator who started his career at Walt Disney Studios, where he was an effects animator on Pinocchio and Fantasia.  In 1942, McDermott enlisted in the U.S. Marines and served as a combat artist.  He later described World War II as being his art education.  After the war, he worked as a freelance illustrator and his work appeared on the covers of several pulp magazines and novels.  Under the name J.P. Ryan, he also worked as a writer.  His experiences at Disney inspired his 1971 novel, The Rat Factory.

The first two illustrations below are examples of the work he did while in the Marines.  The rest are from his career in the pulps: