The history of radio:

The 90th anniversary of commercial radio

Frank Conrad's 75 watt experimental transmitter
KDKA Harding-Cox election returns newscasters
Photo courtesy Westinghouse Nuclear

Frank Conrad's 75 watt experimental transmitter
Frank Conrad's experimental transmitter
Photo courtesy Nuts and Volts

The first commercially licensed radio station went on the air at Pittsburgh, Pennsylvania, ninety years ago on November 2, 1920.

The experimental transmitter licensed as amateur station 8XK had existed since 1916 in Westinghouse engineer Frank Conrad's garage in the Pittsburgh suburb of Wilkinsburg. Conrad had moved it to a shed atop Building K of the Westinghouse East Pittsburgh works, licensed it using the callsign KDKA from the U.S. registry of maritime stations, and used it to make regularly-scheduled broadcasts.

The first broadcast featured presidential election night coverage from 6:00 p.m. until noon the following day as U.S. Senator and newspaper publisher Warren G. Harding from Ohio beat Ohio Governor James M. Cox for the U.S. presidency.

Amidst the election news reports and musical interludes, KDKA's announcers asked the audience, "Will anyone hearing this broadcast please communicate with us, as we are anxious to know how far the broadcast is reaching and how it is being received." The broadcast was said to have been heard as far away as Canada.

KDKA continues on the air today.

More information:
On the Web: KDKA
Wikipedia: KDKA AM
Wikipedia: The 1920 Election
STO: The History of Radio at a Glance