Lutheran hour. Walter was first speaker in 1930.1906, first broadcast was him on a violin playing oh holy night. Harding Cox election.
Early on, NBC gave free air time to "the three religions on America; Catholic, prodestant, and Jewish. We had to share with ....cabin, a prodestant broadcast. Another radio station, CBS, gave us a spot Thursday nights. They almost stopped it. The people in New York said the sermons could only be 15 minutes long. Mail started pouring in due to the novelty of a sermon Midwest. Eventually the people at CBS said, you can speak as long as you want, due to the public support.

The Lutheran Hour was off the air for a few years, but the idea whenever lost. 1931 to 1935.

The announcer introducing the Lutheran Hour was the Lone Ranger's voice for a while.  

It was the largest religious mail receiver radio broadcast from 1935 on... (if I heard right)