AM radio travels farther than FM radio, but FM radio has better sound quality. This means that AM radio can appeal to vast, low population density areas and is best used as a talk radio platform, while FM radio is a better fit for music stations and dense, urban/suburban areas.

These divergent audiences have had a commanding impact on the programming available. Today AM is mainly the preserve of talk radio, news, sports, religious programming, and minority language broadcasting including some types of minority interest music.

That said, AM radio was not always as niche as it is today. The Golden Age of Radio from 1920s to 1940s connected rural America to the outside world. Many an evening was spent listening to radio plays, serial mysteries, soap operas, quiz shows, variety hours, situation comedies, children's shows, news, and FDR's famous fireside chats.

FM radio was adopted later and more slowly than AM radio. Cars began to adopt AM radio receivers in the 1930s and FM receivers were adopted in the 1950s and 1960s. FM stations began broadcasting in the late 1930s, but it was not until 1978 that listenership to FM stations exceeded that of AM stations in North America. During the 1980s and 1990s, Top 40 music stations and later even country music stations largely abandoned AM for FM.

From 1949 to 1987 the FCC had broad authority to regulate broadcast communications under the "Fairness Doctrine". This policy relied heavily on voluntary compliance, to such an extent that in 1974 the FCC reported that they had yet to exercise their authority! Nevertheless, with listenership declining in the 1980s and the burdensome yoke of FCC regulation removed, AM stations were in need of new programming. In the late 80s/90s AM radio found that renewed vigor from a new programming format that has sustained it ever since: conservative talk radio.