McCarthy began his art career as a commercial illustrator, opening his own studio in 1948. He did illustrations for most of the paperback book publishers, magazines, including Colliers, Argosy, and True,[4] movie companies, and advertisements.
McCarthy left the commercial art world in 1968 in order to concentrate on Western paintings. In 1975 he was invited to join the Cowboy Artists of America.[5] His 1972 painting "The Last Crossing" was used by The Marshall Tucker Band in 1976 for the cover of their fifth studio album, Long Hard Ride. He was inducted into the Society of Illustrators Hall of Fame in 1997.