The above photo shows radio station 8MK in Detroit, Michigan going on the air August
20, 1920. The Station was located in the Detroit News Building, a common practice in
the early days of radio. The first news program was broadcast August 31, 1920. The station was later renamed WWJ and is still broadcasting at 950 on the AM dial with
a all-news format under the ownership of the CBS network.

Listening to a ready-made radio receiver in 1920

It is generally agreed that the first paid radio commercial was developed by 
WEAF in New York by AT&T in August of 1922. The book titled "The WEAF
Experiment" by an AT&T employee describes the concept of "toll broadcasting"
to advertisers, in which businesses would underwrite or finance a broadcast, in
exchange for being mentioned on the radio. The first sponsor, or commercial –
according to AT&T – came from the Queensboro Reality Corporation of New
York, advertising an apartment complex. The set of five programs over five
days starting 8/28/22 cost $50, plus the long distance access fee.

Robert Young and Jean Vander Pyl on the air with Father Knows Best

The series “Father Knows Best” began August 25, 1949, on NBC Radio. It
starred Robert Young as Insurance agent Jim Anderson. His wife Margaret
was originally portrayed by June Whitley and later by Jean Vander Ply
(shown above). The Anderson children were Betty (Rhoda Williams), Bud
(Ted Donaldson), and Kathy (Norma Jean Nillson). The cast also included
Eleanor Audley, Herb Vigran and Sam Edwards. The show was sponsored
for most of its run by General Foods and was heard Thursday evenings
until March 25, 1954. The show went to TV in 1954.

Mae West was a actress, playwright, screenwriter and sex symbol who
who known for her bawdy type language. She made a name for herself
in Vaudeville and on the stage in New York before moving to Hollywood
to become a comedienne in the motion picture industry. West was one
of the more controversial movie stars of her day, encountering many
problems including censorship. When her film career ended, she
continued to perform on stage in Las Vegas and on radio and
television.

A routine called "Doughnut Dunkers"  led to comedian Red Skelton’s first network
radio appearance on The Rudy Vallee Show on August 12, 1937. The program
had a talent show segment and those who were searching for stardom were eager
to be heard on it. The show received enough fan mail after Skelton’s performance
to invite him back two weeks after his initial appearance and again in November of
that year. On October 1, 1938, Skelton replaced  Red Foley as the host of Avalon
Time on NBC. Skelton continued as the show’s host until late 1939, when he went
on to begin his MGM movie career.

Radio show host Rudy Vallee with a young talent constant