Jack Kirby, born Jacob Kurtzberg, was a product of the Lower East Side slums. “My mother once wanted to give me a vacation,” he said, describing his childhood, “so she put me on a fire escape for two weeks and I was out in the open air sleeping for two weeks on a fire escape and having a grand time.” A member of the Suffolk Street Gang, as a youth he was no stranger to the rougher elements of his neighborhood (“I would wait behind a brick wall for three guys to pass and I’d beat the crap out of them and run like hell”), but Kurtzberg found his escape in fantasy: in Shakespeare, in movie matinees. The life-changing moment was the rainy day he saw a pulp magazine with an illustration of a foreign-looking, futuristic object on the cover, floating down the gutter. He picked up the copy of Wonder Stories and stood transfixed, staring at this thing called a rocket ship. Kurtzberg threw himself into drawing his own stories, carefully studying the comic-strip artistry of Milton Caniff’s Terry and the Pirates, Hal Foster’s Tarzan, and Billy DeBeck’s Barney Google.

Text from Marvel Comics: The Untold Story

Jack Kirby illustration for Marvel Stories #2, November 1940. This was published about four months before the first issue of Captain America.

Cover here: http://www.pulpsandcomics.com/dtaweb2/U2-87-110.jpg