The earliest radio stations were simply radiotelegraphy systems and did not carry audio. The first claimed audio transmission that could be termed a broadcast occurred on Christmas Eve in 1906, and was made by Reginald Fessenden. While many early experimenters attempted to create systems similar to radiotelephone devices where only two parties were meant to communicate, there were others who intended to transmit to larger audiences. Charles Herrold started broadcasting in California in 1909 and was carrying audio by the next year.

For the next decade, radio tinkerers had to build their own radio receivers. KDKA AM of Pittsburgh, Pennsylvania (owned by Westinghouse) started broadcasting as the first licensed "commercial" radio station on November 2, 1920[citation needed]. The commercial designation came from the type of licensethey didn't start airing advertisements until a few years later. The first broadcast was the results of the U.S. presidential election, 1920. The Montreal station that became CFCF-AM began program broadcasts on May 20, 1920, and the Detroit station that became WWJ began program broadcasts beginning on August 20, 1920, although neither held a license at the time.

Radio Argentina began regularly scheduled transmissions from the Teatro Coliseo in Buenos Aires on August 27, 1920, making its own priority claim. The station got its license on November 19, 1923. The delay was due to the lack of official Argentine licensing procedures before that date. This station continued regular broadcasting of entertainment and cultural fare for several decades.

When internet based radio became feasible in the mid '90s, the new medium required no licensing and the stations could broadcast from anywhere in the world without the need for "over the air" transmitters. This greatly reduced the overhead for establishing a station, and in 1996, George Maat started 'A' Net Station (A.N.E.T. and began broadcasting commercial free from Antarctica.

MIT developed the "Radio Locator" List of Radio Stations. After stations started streaming audio on the internet, Radio-Locator added this to their search engine so anyone could locate a station's website and listen to a station offering a worldwide stream. This list also tracks "terrestrial" radio stations who may not have live audio on the net, or even a website, but are able to find station information by various other search queries.

Types

The best known are the AM and FM stations; these include both commercial, public and nonprofit varieties as well as student-run campus radio stations and hospital radio stations can be found throughout the developed world.

Although now being eclipsed by internet-distributed radio, there are many stations that broadcast on shortwave bands using AM technology that can be received over thousands of miles (especially at night). For example, the BBC has a full schedule transmitted via shortwave. These broadcasts are very sensitive to atmospheric conditions and sunspots.

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