
Marvel Comics
Founded by Martin Goodman as Timely Publications in 1939, the Marvel imprint began in 1961 featuring such superheroes as the Fantastic Four, Spider-Man, Captain America, and the X-Men.
The Avengers Featuring Captain America
The Avengers, no. 16, May 1965. New York: Marvel Comics. Stephen A. Geppi Collection of Comics and Graphic Arts, Serial and Government Publications Division, Library of Congress (015.00.00) © Marvel Worldwide, Inc.

DC Comics
Detective Comics, Inc. launched Superman with Action Comics #1 in 1938, beginning a superhero empire that has grown to include Batman and Robin, and Wonder Woman.
Wonder Woman
Wonder Woman, no. 329, February 1986. New York: DC Comics. Stephen A. Geppi Collection of Comics and Graphic Arts, Serial and Government Publications Division, Library of Congress (013.00.00) © DC Comics