You may have wondered why most radio and TV stations have their call letters begin with a W or a K.  It’s because those letters were assigned to American airwaves by an international convention held in London in 1912.  We also got A and N, but those were reserved for the Army and Navy.  Canada gets a C. 
Radio had a pretty rough start.  People really didn’t much think there was any use for radio when it first debuted.  Most folks thought that talking to your neighbor over the fence was a pretty good way to get the local gossip, and the newspapers were in their glory days.  So, radios weren’t selling very well at all.  In 1921, only one in every 500 homes even owned a radio. 

But, it took one big event to get radio off the ground.  That event was the Dempsey-Carpentier heavyweight championship fight in July of 1921.  It was a fight was so huge that the New York Times devoted almost the entire first 13 pages of the paper to it.  The interest got so great that somebody got the idea it would be a good thing for radio.
When people found out they could hear the fight on radio, sales exploded.  The problem was many stores quickly ran out of them because they didn't have many in stock.  So people gathered around in groups to hear the fight.  One person listened, and would yell out to the crowd what was happening.  Huge crowds gathered everywhere in the country, usually around a store with a radio. 

After that fight, pretty much everyone wanted a radio of their own.  Within the next two years, four million radios were sold.  Sales of radios climbed to $850 million by the end of the decade - all because of a boxing match.

SOURCES: The Wireless Age, Early Radio History