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. Over the years, an estimated 210 million copies of "Captain America" comic books have been sold in a total of 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.
Source: Wikipedia, "Captain America," available under the CC-BY-SA License.