It was nearly 100 years ago that an engineer named Dr. Frank Conrad decided to stick a mike a front of his phonograph and send the signal out over the radio transmitter he had built in his garage. Conrad’s Saturday night broadcasts not only gave rise to the first commercial radio station in the U.S. (KDKA Pittsburgh) but the Westinghouse employee was setting the tone for what would be the predominate type of programming over the airwaves for decades, music.

In the early years of radio, when most shows were local, the music came from wherever broadcasters could find it. According to Leonard Maltin, author of The Great American Broadcast, “In the earliest days of broadcasting, almost everyone who could sing or play an instrument found a home on radio.”

That began to change with the advent of radio networks, NBC in 1926 and CBS in 1927. The plethora of local stations were connected into networks and their programming began to dominate the airwaves. What didn’t change was the importance of music as a part of that programming. NBC’s first broadcast was a live event at the Waldorf Astoria which featured an orchestra, an opera and dance bands. Music continued to be the most popular form of radio programming throughout the 20’s. In addition to symphonies and opera, radio introduced wider audiences to jazz.

Almost all the music on radio, even as late as the mid-1940’s was performed live. The record industry and the artists themselves were opposed to playing recorded music on radio for fear it would impact record sales. They were about as successful as the recording industry would be decades later when they tried to stop MP3s. Recording tape was not invested until the 40’s. The first pre-recorded radio program was Bing’s Philco Radio Time in 1946.

But music was not the only way to find an audience in the ether and stations were quick to catch onto the attraction of sports. One of the first big sporting events on radio was the Jack Dempsey-Georges Carpentier heavyweight championship fight in 1921. Receivers were placed in theaters and it is estimated that some 300,000 heard the call of the match. David J. Halberstam, author of Sports on New York Radio, believes “boxing is not only the root of sports on radio but it is the very root of all radio.” Of the Dempsey-Carpentier fight he says: “The experiment was such a smash success it resulted in the proliferation of radio stations and the spiraling of radio receivers.”

In 1927, the second championship fight between Gene Tunney and Jack Dempsey held at Soldier Field in Chicago drew a network listening audience of 50 million. To appreciate how popular heavyweight boxing was on radio, consider that the most recent World Series between the Cubs and the Indians, one of the most widely viewed baseball games in decades, drew a viewing audience of 40 million.

Other sports were also quick to find their way onto radio. KDKA broadcast the Pittsburgh-West Virginia college football game in 1921. That same year WJZ New York aired the Yankees-Giants World Series. Throughout the 20’s, 30’s and into the 40’s the most popular sports on radio were boxing, college football and baseball. And the biggest events were heavyweight championship fights, the Rose Bowl and the World Series.

In took a little bit longer for news to catch on. Radio gradually became the go to medium for important events. KDKA, already a pioneer in music and sports broadcasting, covered the Harding-Cox presidential election in 1920. In 1927, the new NBC network put together 50 stations and drew 15 million listeners for the Charles Lindbergh ticker tape parade. Two events in 1932 helped propel radio into the forefront of news media: one was the Hoover-Roosevelt election and the other was the kidnapping of Lindbergh’s baby. Until that time the newspaper “extra” edition was the primary source of breaking news. Radio disrupted that. By 1941 when FDR made his “day that will live in infamy speech” following the attack on Pearl Harbor, it is estimated that 79% of all American homes were listening on radio.

Some other changes in the popularity of programming began to appear in the 30’s. Some attribute this to the Depression causing American listeners to look to the radio for some escape from hard times. Others see it as a reflection of the fact that network programs were generally produced and controlled by advertisers. What they found is that nothing drew a bigger audience in the 30’s than comedy. The first comedy to achieve a mass audience was Amos ‘n’ Andy, a show that was based on demeaning racial stereotypes. It was also the most popular show in the nation by 1929. At one point Amos ‘n’ Andy reached 40 million listeners, about one-third of the entire U.S. population.

Many other comedy shows echoed vaudeville. Well-known comedians like Jack Benny and Burns and Allen, who later went on to TV stardom, got their start in radio.

Another popular form of programming was drama. Two of the early dramatic series were Roy Rogers and Sergeant Preston, both of which came on the air in the late 20’s. Radio also presented condensed versions of novels, plays and even popular movies. Soap operas came to dominate daytime listening. WGN in Chicago introduced the first daytime radio soap, Painted Dreams, in 1930.  It lasted until 1943. And the first quiz show, Professor Quiz, made its debut in 1936.

This mix of sitcoms, live sports, adventure series, daytime dramatics and game shows is exactly what television would offer when it started to come into widespread use in late 1940’s and 1950’s. To this day, many of the types of programming that you see on TV had their origins during the heyday of radio.

While sports and news continue to have some place on radio, once the cowboys, the comedians and the weepy jilted lovers moved over to TV, they disappeared from the radio dial. And that sent radio back to its roots, music.  The authors of Last Night a DJ Saved My Life note that “By the fifties, broadcasters had finally settled most of their disputes with the wider music industry and there were no more legal obstacles to filling airtime with records. The transistor had been invented in 1948, so a radio receiver could now be cheap and portable. And around the same time society invented the teenager.”

All that translated into a new era of radio personalities, DJ’s. Just as radio had found a mass audience for jazz in the 20’s, it introduced many Americans to rhythm and blues and rock ‘n’ roll in the 50’s. According to Listening In author Susan J. Douglas. “Perhaps radio’s most revolutionary influence on American culture and its people was the way it helped make music one of the most significant, meaningful, sought after, and defining elements of day-to-day life, of generational identity and of personal and public memory. Radio gradually made music available to people at most times of the day and night.”