Captain America is a fictional character, a superhero that appears in comic books published by Marvel Comics. The character first appeared in Captain America Comics #1 (cover-dated March 1941), from Marvel Comics' 1940s predecessor, Timely Comics, and was created by Joe Simon and Jack Kirby. As of 2007, an estimated 210 million copies of "Captain America" comic books had been sold in 75 countries. For nearly all of the character's publication history, Captain America was the alter ego of Steve Rogers, a frail young man who was enhanced to the peak of human perfection by an experimental serum in order to aid the United States war effort. Captain America wears a costume that bears an American flag motif, and is armed with an indestructible shield that can be thrown as a weapon.
An intentionally patriotic creation who was often depicted fighting the Axis powers of World War II, Captain America was Timely Comics' most popular character during the wartime period. After the war ended, the character's popularity waned and he disappeared by the 1950s aside from an ill-fated revival in 1953. Captain America was reintroduced during the Silver Age of comics when he was revived from suspended animation by the superhero team the Avengers in The Avengers #4 (March 1964). Since then, Captain America has often led the team, as well as starring in his own series.
Steve Rogers was purportedly assassinated in Captain America vol. 5, #25 (March 2007), although he was later revealed to be alive. The comic-book series Captain America continued to be published, with Rogers' former sidekick, James "Bucky" Barnes, having taken up the mantle, and keeping it at the insistence of Rogers, who upon his return began operating as an intelligence agent in the Secret Avengers title, and in the limited series Steve Rogers: Super Soldier, before resuming the identity after Bucky was killed in the line of duty.