Who was the first actor to play "Superman" on the radio?

The serial came to radio as a syndicated show on New York City's WOR on February 12, 1940. On Mutual, it was broadcast from August 31, 1942, to February 4, 1949, as a 15-minute serial, running three or, usually, five times a week. From February 7 to June 24, 1949 it ran as a thrice-weekly half-hour show. The series shifted to ABC Saturday evenings on October 29, 1949, and then returned to afternoons, twice-a-week on June 5, 1950, continuing on ABC until March 1, 1951. In all, 2088 original episodes of The Adventures of Superman were aired on American radio.

Created by Jerry Siegel and Joe Shuster, the Man of Steel first appeared in Action Comics #1 in 1938. The following year, the newspaper comic strip began and four audition radio programs were prepared to sell Superman as a radio series. When Superman was first heard on radio less than two years after the comic book appearance, the character took on an added dimension with Bud Collyer in the title role. During World War II and the post-war years, the juvenile adventure radio serial, sponsored by Kellogg's Pep, was a huge success, with many listeners following the quest for "truth and justice" in the daily radio broadcasts, the comic book stories and the newspaper comic strip.