This is a volume of history validating the contributions of radio toward keeping America informed. Like everything else, radio has gone through many changes since the 1920s. Periods very distinct from each other embrace its roots, its golden age, and the well-defined eras dominated by the disc jockey, talk, and news formats. The U.S. was dependent on radio as a source of cheap entertainment during the Great Depression and the critical information gained from it during the Second World War had no parallel. Radio's diminished effects in the wake of television in the 1950s are surveyed; the aural medium shifted from being at the core of many families' activities to more specialised applications, reaching narrowly defined listener bases. Many people turned elsewhere for the news. (And now even TV is challenged by yet newer media.) The introduction of technological marvels throughout the past hundred years has significantly altered what Americans hear and how, when, and where they hear it.