|Marconi made the first usable radio in 1895 and bandwidth in America was first regulated by the Radio Act of 1912. This was not done to protect "entrenched interests".|
1.) Radio operators in the US had to obtain a license from the US Department of Commerce and Labor but a radio license generally could not be withheld.
2.) All commercial seagoing vessels were required to constantly monitor distress frequencies. (the Titanic sank in April of 1912)
Herbert Hoover was Commerce Secretary from 1921 to 1928, with the new FRC (Federal Radio Commission) in 1926 continuing to operate under the Department of Commerce. Hoover became President in 1929.
Prior to 1926 Herbert Hoover personally allocated radio spectrum and was instrumental in promoting radio usage.
A year later in 1927 the FRC began to reallocate spectrum telling 164 radio operators to justify their existence or lose their license.
The first legal fight over loss of spectrum was filed by KFKB in Kansas. - en.wikipedia.org - The FCC was created in 1934 by Congress to replace the FRC.
KFKB Milford, Kansas,  had been renewed several times by the Federal Radio Commission. It was one of the most popular stations in the nation. KFKB was owned by a surgeon, John R. Brinkley, who, among other things, espoused, over the airwaves, implanting slivers of goat testes in men's testicles for "sexual rejuvenation." The American Medical Association was very upset over a program in which he read listener mail describing symptoms, and then prescribed over the air, describing the medication by number. Listeners had to visit a Brinkley "kick back" pharmacy to fill these prescriptions.
In 1930 the Federal Radio Commission denied his request for renewal. Brinkley appealed on the grounds of censorship. The U.S. Court of Appeals denied his appeal. The court ruled that the Federal Radio Commission could consider past programming content without it being censorship. This, however, didn't stop the ever-popular Dr. Brinkley, who almost won the governorship of Kansas in 1930 by write-in votes.
Brinkley finally beamed his programs to the United States over 100,000 watt XER from Villa Acuna, Coah, Mexico. This was twice the power of any broadcast radio station save one experimental 500,000 watt station, WLW Cincinnati. Not to be outdone, Brinkley increased his power to 500,000 watts as well, as XERA, and used a curtain-array antenna to focus his signal northward.  In 1941, Brinkley suffered from a series of serious medical problems. During his attempt to recuperate from them, he was charged with mail fraud, but died before the case could be tried. 
This was the US spectrum allocation as of 2016. - upload.wikimedia.org