In Flash Comics #104 (December 1948), the Rival makes his first appearance. Though he is not the first evil speedster, he is the first recurring evil speedster and the first to style himself after The Flash. Dr. Edward Clariss worked on a chemical formula to give himself temporary superspeed after learning that the Flash was a student of his college back in 1940. Jay Garrick overcomes the Rival and sends him off to prison, but…
This issue of Flash Comics is also notable as the last appearance of the Golden Age Flash, Hawkman and Atom outside of the Justice Society appearances. Flash Comics would be later reborn ten years later, continuing the numbering, but with the Silver-Age Flash. Flash Comics is the first major superhero comic to be cancelled in the Golden Age.