ACTION COMICS #1
No, he couldn't fly — hence the "leaping a tall building in a single bound" — but so much of Superman's mythology was firmly in place in Jerry Siegel and Joe Shuster's very first Superman story: the baby sent from a dying planet to Earth, being raised as a human, an older Clark Kent falling for a woman named Lois Lane. The modern age of the superhero can be traced back to this 1938 issue.