Following is the daily "Profile America" feature from the U.S. Census Bureau:
FIRST LICENSED RADIO STATION
Profile America — Saturday, August 20th. The nation's first radio station licensed by the federal government began broadcasting in Detroit on this date in 1920 — station 8MK, now operating as WWJ. The station was owned by the Detroit News, and operated with an amateur license, which in 1922 was changed to commercial. The first station to receive a commercial license was KDKA in Pittsburgh, which began broadcasting in October of 1920. From these rudimentary early broadcasts, the new medium grew rapidly. In 1922, there were 30 radio stations, but by the following year, there were 556. Now, there are nearly 15,500 AM and FM radio stations across the U.S., along with just over 1,500 low-power FM facilities. Profile America is in its 20th year as a public service of the U.S. Census Bureau.
Sources: Kane's Famous First Facts, 6294
8MK/accessed 5/16/2016: www.michiguide.com/history/am.html
Licensing/accessed 5/16/2016: http://www.oldradio.com/archives/stations/wwj1.htm
Early station totals: Historical Statistics of the United States: Colonial Times to 1970, p. 796
Station totals 2015/accessed 5/16/2016: https://apps.fcc.gov/edocs_public/attachmatch/DOC-338754A1.docx
Profile America is produced by the Center for New Media and Promotion of the U.S. Census Bureau. Statistics and accounts drawn from cited non-Census sources are employed for illustrative or narrative purposes, and are not attested to by the U.S. Census Bureau. These daily features are available as produced segments, ready to air, on the Internet at http://www.census.gov (look for "Audio" in the "Library" pull-down menu).
Source : prnewswire.com