For three decades starting in 1920, radio revolutionized American culture.

At a time when most citizens still lived outside of big cities, radio technology—which allowed sound signals to be transmitted across long distances—made the sprawling nation feel smaller and more connected. And it grew like wildfire: In the 1930s, radio ownership doubled, from about 40 percent of U.S. families at the decade’s start to nearly 90 percent by 1940—more than had cars or indoor plumbing, according to historian Bruce Lenthall, author of Radio’s America: The Great Depression and the Rise of Modern Mass Culture.

Radio fostered a real-time national conversation during challenging times of Depression and world war. And it became the single greatest force (before television and the internet) in developing a mass culture of sports, entertainment, news and advertising.

Delivering the wider world with a greater immediacy and intimacy than ever before, it joined listeners of every age, race and class—in every corner of the country—around their wireless boxes. Author and essayist E.B. White, writing in 1933, called the radio an almost “godlike presence” in his rural community.

Below, find eight of the most seminal moments in radio—from KDKA’s pioneering live broadcast of 1920 presidential election results to Edward R. Murrow’s live nighttime reports under Nazi bombfire to baseball’s 1951 “Shot Heard ‘Round the World.”

1. 1920: First Broadcast: 1920 Presidential Election Results

When Pittsburgh's KDKA aired live returns from the presidential election race between Warren Harding and James Cox, it delivered the world's first commercial radio broadcast, according to the Federal Communications Commission, which regulates radio and TV in the U.S. Lasting 18 hours, from 6 p.m. on November 2 until noon the next day, the transmission was something of a makeshift affair. KDKA, owned by the Pittsburgh-based Westinghouse Corporation, had received its broadcast license just six days before the election. And the returns were beamed with a 100-watt transmitter from a small shed atop the highest building in Westinghouse’s East Pittsburgh plant.

While the broadcast reached only an estimated 1,000 listeners, it revolutionized how news could be delivered—as it happened in real time, instead of through newspapers printed and distributed hours or days later. And it inspired KDKA to more radio firsts: The following year, in August 1921, the station would air the first live, play-by-play broadcasts of a professional baseball game (Pittsburgh Pirates vs. Philadelphia Phillies) and two months later, a college football match (West Virginia University vs. University of Pittsburgh).

On the four-year anniversary of the election broadcast in 1924, The New York Times reported that KDKA’s 1920 broadcast experiment—enabled by the technological innovations of Guglielmo Marconi and Nikola Tesla—had started something big. Within a few years, more than 530 broadcasting stations had sprung up in the United States, reaching an estimated 10 million people.

2. 1925: The Grand Ole Opry Spreads Country Music

Bluegrass singer songwriter Bill Monroe performs with Jimmy Martin (Buddy Killen on Bass, Don Slayman on fiddle) on stage at the Grand Ole Opry in 1951 in Nashville, Tennessee.
Bob Grannis/Getty Images
Bluegrass singer-songwriter Bill Monroe performs with Jimmy Martin on guitar, Buddy Killen on bass and Don Slayman on fiddle on stage at the Grand Ole Opry in 1951 in Nashville, Tennessee.

In late November of 1925, in a new show called “Barn Dance” on Nashville's WSM radio station, announcer George D. "Judge" Hay introduced the program’s first-ever performer: octogenarian fiddler Jimmy Thompson playing foot-tapping, old-time music with his niece on piano accompaniment. Two years later, Hay changed the name of the show to the “Grand Ole Opry,” signaling in an on-air riff that they would offer a homier style of music than the grand opera show that preceded it on air each week.

Sears-Roebuck, a key KSM advertiser, initially opposed what it called the show’s “disgraceful low-brow music,” but fan letters poured in. By 1930, the Opry had 30 regular cast members, and WSM built a 500-seat studio theater to handle what was quickly becoming as much a live event as a radio broadcast. In 1932, WSM boosted its broadcast power to 50,000 watts, extending its reach to most of the U.S. and parts of Canada, and allowing country music to grow in popularity. The show introduced the world to bluegrass and country legends from Bill Monroe to Hank Williams to Dolly Parton.

“In a very real sense, the history of the Grand Ole Opry radio broadcast is the history of commercial country music,” wrote David Bruenger in Making Money, Making Music: History and Core Concepts. “Everything we know today about the Nashville sound, Nashville publishing, record labels and celebrities is the result of the opportunism and reach of this amazing show.”

3. 1933-1934: FDR’s Fireside Chats Soothe a Jittery Nation

Between March 1933 and June 1944, through Depression and war, President Franklin D. Roosevelt gave 30 speeches where he spoke directly to millions of Americans through a radio broadcast. These speeches became known as the "fireside chats,” a term coined by CBS station manager Harold Butcher because of President Roosevelt’s conversational speaking style. The first one began: “I want to talk for a few minutes with the people of the United States about banking.”

Prior presidents had depended primarily on newspapers to communicate their messages. During World War II, Roosevelt used his chats to provide frequent updates on the conflict, unfiltered by the media. According to a White House historian Margaret Biser, Roosevelt was frustrated with the press throughout his presidency. When a reporter asked him if he planned to discuss recent talks with Winston Churchill on air, Roosevelt said, “It’s up to you fellows. If you fellows give the country an exceedingly correct picture, I won’t go on the radio.”

While the chats appeared to be conversational and improvised, Biser said that they were fact-checked and re-written several times by a team of speechwriters and that Roosevelt spoke more slowly than most radio announcers of the era, using an average of 65 fewer words per minute.

“Radio provided a connection between Roosevelt and the people,” wrote Celeste Nunez, a scholar of the 32nd president’s “fireside” addresses. His accessible style allowed Americans to "easily grasp why Roosevelt installed the programs he did and understand the actions of his administration.”

4. 1938: The ‘Fight of the Century’ Reaches the Largest Radio Audience in History

For their first fight on June 19, 1936, Black American boxer Joe Louis was a 10-to-1 favorite over Max Schmeling, but the German won the fight in a 12th-round knockout at Yankee Stadium. In the rematch two years later, Louis got his revenge with a technical knockout in the first round.

It's hard to underestimate the cultural impact of this sporting event. Fought against the backdrop of increasing Nazi aggression in Europe, the second fight is believed to have had the largest audience in history for a single radio broadcast—with an estimated 70 million listeners, according to the Library of Congress, which selected it in 2005 for its National Recording Registry.

5. 1941: The Attack on Pearl Harbor is Reported Live

As the Japanese attacked the U.S. naval base at Pearl Harbor on December 7, 1941, an unknown KTU reporter in Honolulu explained what was happening in real time:

The reporter, transmitting his report through phone lines to NBC in New York, was providing the nation with the only live broadcast of the surprise Pearl Harbor attack. At the time of the ferocious WWII air assault—which killed more than 2,400 Americans, damaged or destroyed nearly 20 naval vessels and more than 300 aircraft—there were 45 million radios in the United States. Around the nation, millions had their regularly scheduled programs interrupted by the historic news that the war had arrived on American shores.

6. 1938: 'The War of the Worlds' Airs; Panic Ensues

On the night of October 30, 1938, between 8:15 and 9:30 p.m., a radio dramatization of H.G. Wells' sci-fi fantasy novel The War of the Worlds, performed by 23-year-old Orson Welles' Mercury Theatre, sent thousands of Americans into a frenzy. After hearing the broadcast, many believed that an interplanetary conflict had started with the invasion of Martians spreading death and destruction in New Jersey and New York.

Reporting the day after the broadcast, The New York Times said that, in Newark, on a single block, more than 20 families left their homes with handkerchiefs and towels over their faces to flee what they believed was a gas raid. The “wave of mass hysteria” that the Times described in its report was challenged in The Invasion from Mars: A Study in the Psychology of Panic, published in 1940 by Hadley Cantril from Princeton University’s Radio Research Project. According to Cantril, of the 6 million who heard the broadcast, at least 1 million believed it to be true.

In 2015, Brad Schwartz, a Princeton Ph.D student, studied letters that citizens wrote to radio stations at the time to provide a new appraisal of the episode. In his Broadcast Hysteria: Orson Welles’s ‘War of the Worlds’ and the Art of Fake News, Schwarz discovered that the vast majority of people were not frightened by the broadcast. “Many feared that democracy simply couldn’t survive in an age when the mass media could lie so convincingly,” Schwartz said in a 2018 interview, "and they wrote to save Welles from the possibility of government censorship.”

7. 1951: The ‘Shot Heard Round the World’ Leaves Sportscaster Sputtering

The 1951 National League pennant game at New York's Polo Grounds between the Brooklyn Dodgers and the New York Giants may have been the first-ever nationally televised broadcast baseball game—but it’s best known for the radio broadcast. The dramatic moment came in the final game of a three-game, winner-take-all series. The Giants were down 4-2 in the 9th inning when Bobby Thompson came up to bat with runners on second and third base.

Russ Hodges' call on WMCA of Thompson's pennant-clinching three-run homer is one of the most memorable radio moments of the 20th century:

In 2020, Hodges’s iconic call of the Thomson home run was selected by the Library of Congress for inclusion in the National Recording Registry.

8. 1939-1941: Edward R. Murrow Reports the Bombing of London

Between 1939 and 1941, CBS News Radio correspondent Edward R. Murrow's dramatic live reports from London during World War II made the horrors of war immediate and visceral. On September 21, 1940, as Nazi Germany bombed London, Murrow transmitted this gripping report from a rooftop:

For millions who followed the war in Europe from the safety of their homes an ocean away, Murrow's word pictures—accompanied by thudding bombs, snapping antiaircraft guns and shrieking whistles—helped generate support for the necessity of America's entering the war and aiding Allied forces against Nazi aggression.

“Murrow brought World War II into the living rooms of American homes,” wrote Bob Edwards, the former NPR reporter and author of Edward R. Murrow and the Birth of Broadcast Journalism. “Rarely had people heard the sounds of actual war unless they had fought in one themselves. To hear the shooting along with Murrow's outstanding reporting was something new and exciting. It established radio's place as a legitimate source of journalism.”


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