Mel began his radio career in 1927 as a voice actor on a program called The Hoot Owls. He moved to Los Angeles for a short time and it was there that he met Estelle Rosenbaum. Mel and Estelle married in 1933 and they moved to Mel's hometown, Portland where they produced and hosted a program called Cobwebs and Nuts. The show lasted for two years before Estelle encouraged Mel to move back to Los Angeles.
It was this second move to Los Angeles that would give Mel steady work and make him the most sought after voice actor in radio. He would work for Warner Brothers, then CBS, but it was his work on The Jack Benny Program on NBC that would really make him famous.
On The Jack Benny Program Mel provided the voice for Jack Benny's old, rundown car Maxwell, his violin teacher Professor LeBlanc, Polly the Parrot, Jack's pet polar bear Carmichael, was cast as the department store clerk, the train announcer, and Sy, the Little Mexican (probably his most famous role on the radio program and the television program as well).
Here is that popular bit on The Jack Benny Show:
Mel's success on The Jack Benny Program led to work on more radio programs like Burns and Allen and Abbott and Costello. He also had a season of his own program called The Mel Blanc Show.