Captain America Comics #1, containing the first appearance of the superhero Captain America, is published.

Captain America Comics is a comic book series featuring the superhero character Captain America. The series was originally published by Timely Comics from 1941 to 1950, with a brief revival by Atlas Comics in 1954.

Captain America is a superhero created by Joe Simon and Jack Kirby who appears in American comic books published by Marvel Comics. The character first appeared in Captain America Comics #1, published on December 20, 1940, by Timely Comics, a corporate predecessor to Marvel. Captain America's civilian identity is Steven "Steve" Rogers, a frail man enhanced to the peak of human physical perfection by an experimental "super-soldier serum" after joining the United States Army to aid the country's efforts in World War II. Equipped with an American flag–inspired costume and a virtually indestructible shield, Captain America and his sidekick Bucky Barnes clashed frequently with the villainous Red Skull and other members of the Axis powers. In the war's final days, an accident left Captain America frozen in a state of suspended animation until he was revived in modern times. He resumes his exploits as a costumed hero and becomes the leader of the superhero team the Avengers, but frequently struggles as a "man out of time" to adjust to the new era.

December 20 is the 354th day of the year in the Gregorian calendar; 11 days remain until the end of the year.