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KAY GALLANT: While the automobile greatly changed America's transportation, radio greatly changed its communication.

The first radio station opened in the state of Pennsylvania in nineteen-twenty. Within ten years, there were hundreds of others. There were more than thirteen million radio receivers. Most of the radio stations were owned by large broadcasting networks. These networks were able to broadcast the same program to stations all over the country.

MAURICE JOYCE: Most programs were simple and entertaining. There were radio plays, comedy shows, and music programs. But there also were news reports and political events. Millions of people who never read newspapers now heard the news on radio. Citizens everywhere could hear the president's voice.

Like the automobile, radio helped bring Americans together. They were able to share many of the same events and experiences.

KAY GALLANT: Radio also was a great help to companies. Businesses could buy time on radio programs for advertisements. In these 'ads', they told listeners about their products. They urged them to buy the products: cars. Electric refrigerators. Foods. Medicines. In this way, companies quickly and easily created a nationwide demand for their goods.

Automobiles and radios were not the only new technologies to change American life in the days after World War One. Still one more invention would have a great effect on how Americans spent their time and money. That was the motion picture.