When Westinghouse engineer Frank Conrad set up a crude radio studio above his Pittsburgh garage in 1916, placing a microphone in front of a phonograph to broadcast music and news to his friends (whom Conrad supplied with receivers) two evenings a week on experimental station 8XK, he unofficially became one of the medium’s first disc jockeys. In 1920, a Westinghouse executive, intrigued by Conrad’s curious hobby, realized the potential of radio as a mass medium. Westinghouse then established station KDKA, which is generally regarded as the first commercial broadcast station. KDKA is most noted for airing national returns from the Cox–Harding presidential election on November 2, 1920, an event most historians consider the first professional broadcast.

Other amateur broadcasters could also lay claim to being first. One of the earliest stations, operated by Charles “Doc” Herrold in San Jose, California, began in 1909 and later became KCBS. Additional experimental stations—in places like New York; Detroit; Medford, Massachusetts; and Pierre, South Dakota—broadcast voice and music prior to the establishment of KDKA. But KDKA’s success, with the financial backing of Westinghouse, signaled the start of broadcast radio.

In 1921, the U.S. Commerce Department officially licensed five radio stations for operation; by early 1923, more than six hundred commercial and noncommercial stations were operating. Some stations were owned by AT&T, GE, and Westinghouse, but many were run by amateurs or were independently owned by universities or businesses. By the end of 1923, as many as 550,000 radio receivers, most manufactured by GE and Westinghouse, had been sold for about $55 each (about $701 in today’s dollars). Just as the “guts” of the phonograph had been put inside a piece of furniture to create a consumer product, the vacuum tubes, electrical posts, and bulky batteries that made up the radio receiver were placed inside stylish furniture and marketed to households. By 1925, 5.5 million radio sets were in use across America, and radio was officially a mass medium.