Radio broadcasting in the United States is a major mass medium. Unlike radio in most other countries, American radio has historically relied primarily on commercial advertising sponsorship on for-profit stations. The U.S. does not have a national broadcaster that aims its programs at the general public. Nonprofit broadcasting typically comes in three forms: radio evangelism, community radio, and government-subsidized public radio, all of which rely at least to some extent on listener donations. Shortwave broadcasting in the United States includes federal government programs, as well as a limited number of privately managed broadcasts, for overseas audiences. Radio broadcasting became popular in the 1920s, alongside the new film industry. The arrival of television in the 1950s forced radio into a niche role, as leading participants moved into the much larger field of television. In the 21st century, radio has been adjusting to the arrival of the Internet and Internet radio.

Answer this question based on the passage: when did radio become popular in the us? Okie... think carefully first, then make a decision:

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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The relevant information is: Radio broadcasting became popular in the 1920s, alongside the new film industry. So, the answer is the 1920s.