On Sunday, October 30, 1938, Orson Welles broadcast H. G. Wells' War of the Worlds.
Reports in the media afterward described widespread fear and outrage, as people believed that the reading was an actual newscast.
Questions remain as to whether the media hyped the supposed hysteria, but that's how American remembers it.
You can listen to the original radio program here.
It's worth noting that October 30, the day before Halloween, is known as Mischief Night.