Faster than a speeding bullet! More powerful than a locomotive! Able to leap tall buildings at a single bound! Look! Up in the sky! It’s a bird! It’s a plane! It’s Superman! Yes, it’s Superman! Strange visitor from another planet, who came to earth with powers and abilities far beyond those of mortal men. Superman! Who can change the course of mighty rivers, bend steel with his bare hands, and who — disguised as Clark Kent, mild-mannered reporter for a great metropolitan newspaper — fights a never ending battle for truth, justice and the American way!

(Other Authors and Sources)

Preamble to Superman, US radio show (1940ff)