Henry Wilson Allen was born in Kansas City, Missouri. Before he began his writing career he worked variously as a stablehand, shop clerk, and gold miner. In 1937 he began working as a contract screenwriter for MGM animation division. While his early work was for Harman and Ising's "Barney Bear" series, his longest collaboration was with director Tex Avery. Allen was credited as story artist on many classic Avery shorts, included Swing Shift Cinderella, King-Size Canary, and The First Bad Man, among many others. Allen downplayed his contributions to the shorts, claiming that Avery merely used him as a sounding board for his own ideas.

Allen's career as a novelist began in 1952, with the publication of his first Western No Survivors. Allen, afraid that the studio would disapprove of his moonlighting, used a pen-name to avoid trouble. He would go on to publish over 50 novels, eight of which were adapted for the screen. Most of these were published under one or the other of the pseudonyms Will Henry and Clay Fisher. Allen was a five-time winner of the Spur Award from the Western Writers of America and a recipient of the Levi Strauss Award for lifetime achievement.

Allen died of pneumonia on October 16, 1991 in Van Nuys, California. He was 79.