Seventy-five years ago today, radio listeners first heard the immortal words "Up in the sky! Look! It's a bird! It's a plane! It's Superman!" And the rest is pop-culture history.

Within months of his debut in Action Comics #1, Jerry Siegel and Joe Shuter's superhero had already made the leap to newspaper comics pages, but the radio offered DC Comics an opportunity to reach an even larger audience.

Originally titled simply Superman, the long-running serial The Adventures of Superman premiered Feb. 12, 1940, on New York City's WOR AM, and was syndicated to 11 other stations by pre-recorded transcription disks (that number later increased significantly). For 15 minutes a day, three days a week -- the length and frequency of the episodes later increased, too -- kids tuned in to listen to star Clayton "Bud" Collyer, who shifted his voice an octave as he transformed from mild-mannered Clark Kent into Superman with the phrase, "This is a job for SUPERMAN!"

Collyer and Joan Alexander, who played Lois Lane with the character's introduction in the seventh episode, proved so popular that they also lent their voices to the Fleischer animated shorts of the early 1940s, and reprised their roles in Filmation's 1966-'70 animated series The New Adventures of Superman (which also included announcer and Perry White actor Jackson Beck and Jack Grimes, who voiced Jimmy Olsen in the last years of the radio show).

The Adventures of Superman aired a staggering 2,068 episodes, finally coming to an end on March 1, 1951 (by then Michael Fitzmaurice had replaced Collyer), a little more than a year before George Reeves donned the iconic costume for television. In that time, the radio serial introduced such "foundational" elements as Perry White, Jimmy Olsen and kryptonite. It also featured the first World's Finest team-up between Superman and Batman and Robin.

Below, you can listen to the very first episode of The Adventures of Superman, "The Baby from Krypton," courtesy of the Internet Archive.

(via Time)