When was the first major public radio broadcast?

KDKA in Pittsburgh aired a landmark broadcast on 2 November 1920, often cited as the beginning of regular commercial radio broadcasting. The station announced the results of the U.S. presidential election between Harding and Cox. This event demonstrated that radio could be used for mass public communication, not just experiments or point-to-point messages. Radio quickly became one of the most influential media of the 20th century.