Radio is one of the major mass media of the United States.

The beginning of regular commercially licensed sound broadcasting in the United States in 1920 ended the print monopoly over the media and opened the doors to the more immediate and pervasive electronic media. By 1928, the United States had three national radio networks – two owned by NBC (the National Broadcasting Company), and one by CBS (the Columbia Broadcasting System). Until 1943, there were four major national radio networks: two owned by NBC, one owned by CBS, and one owned by Mutual Broadcasting System. The NBC's second network became ABC, the American Broadcasting Company.

Though mostly listened to for entertainment, radio's instant, on-the-spot reports of dramatic events drew huge audiences throughout the Great Depression of the 1930s and World War II. President Franklin D. Roosevelt recognized the potential of radio to reach the American public, and during his four terms (1933–45), his radio "fireside chats" informed the nation on the progress of policies to counter the Depression and on developments during World War II.

After World War II, television's visual images replaced the audio-only limitation of radio as the predominant entertainment and news vehicle. Radio adapted to the new situation by replacing entertainment programs with schedules of music interspersed with news and features, a freeform format adopted by NBC when it launched its popular weekend-long Monitor in 1955. During the 1950s, automobile manufacturers began offering car radios as standard accessories, and radio received a big boost as Americans tuned in their car radios as they drove to and from work.

The expansion and dominance of FM radio, which has better sound quality but a more limited range than traditional AM, represented the major technical change in radio in the 1970s and 1980s. FM radio, aided by the invention of ever smaller portable radios and inexpensive "Walkman" headsets, dominates music programs, while AM has shifted to "talk" and news formats. Talk radio began to ascend in the 1980s, as a result of improvements in satellite communications, the repeal of the Fairness Doctrine, and, by the mid-1990s, extensive concentration of media ownership stemming from the Telecommunications Act of 1996. While prior to the 1980s, talk radio was primarily a local interest, the development of national spoken word programming contributed to the comeback of the once-moribund AM radio. Both FM and AM radio have become increasingly specialized. Music formats, for instance, comprise a variety of specializations—the top five in 1991 being "country and western," "adult contemporary," "top 40," "religious" and "oldies." Radio has also been shaped heavily by demographics, though not quite as much as television; modern radio formats currently tend to target certain groups of people according to age, gender, urban or rural setting, and race. As such, freeform stations with broad-spanning playlists have nearly ceased to exist on commercial radio.

In an era in which TV is clearly the glamour medium, the reach of radio is still extensive. Ninety-nine percent of American households in 1999 had at least one radio; the average is five per household. Every day, radio reaches 80 percent of the U.S. population at one time or another. Revenues more than doubled from $8.4 billion in 1990 to more than $17 billion in 2000. Radio continues to have a hold primarily in automobiles, where attention can be kept on the road while radio is used as background noise.

In 1998, the number of U.S. commercial radio stations had grown to 4,793 AM stations and 5,662 FM stations. In addition, there are 1,460 public radio stations in the United States. Most of these stations are run by universities and public authorities for educational purposes and are financed by public and/or private funds, subscriptions and some underwriting. Public radio broadcasting is mostly by NPR and PBS. NPR (National Public Radio) was incorporated in February 1970 under the 1967 Public Broadcasting Act. PBS was also created by the 1967 Public Broadcasting Act. BBC World Service is distributed is the United States by PRI. It is also possible to listen to BBC World Service via Shortwave radio.

Until the 1980s, most commercial radio stations were affiliated to the large networks, such as Capital Cities/ABC, CBS, Mutual Network, NBC, and others. NBC sold its radio network in 1988. Mutual was purchased by Westwood One. Capital Cities/ABC, later sold to Disney, reduced gradually its radio operations. Nowadays, most commercial radio stations are controlled by media conglomerates like Clear Channel Communications, Infinity Broadcasting and many others.

A new form of radio that is gaining popularity is satellite radio. Sirius XM Radio currently holds a monopoly on the technology after the two entities, Sirius Satellite Radio and XM Satellite Radio, merged into one company. Unlike terrestrial radio music channels, most channels feature few or no commercials. The content of satellite radio is not regulated by the Federal Communications Commission (FCC).

Cable radio, a slightly older technology, has also become widespread. Music Choice is the market leader in this field and specializes in music programming. CRN Digital Talk Radio Networks specializes in talk radio. Cable radio has the distinct disadvantage that it must be hooked to a cable service and/or a television set to work, limiting its use outside the home.

The developments of Internet radio and digital music players, coupled with smartphones with the capability to stream audio, pose a significant threat to terrestrial radio. Unlike satellite radio, most Internet stations do not require a subscription; several of the more popular ones use algorithms that allow listeners to customize the music they want to hear and select new music that may interest them. At the very least, the continued proliferation of Internet-based stations (which are more numerous and easier to set up than their television counterparts) creates a threat of audience fracturing far beyond that currently experienced by television due to cable and satellite.