The first decade of FM broadcasting, starting in 1936 to 1946, occurred in the 42 - 50 MHz band.  The frequency band was changed to the current 88 to 108 MHz band in 1946.  FM stations operating in the old frequency band were required to move to the higher frequencies and most did so before 1948.

Many initial call signs in the FM band were assigned in the following manner:
      an initial "W" or "K", depending on whether the station location was east or west of the Mississippi River,
      followed by two numbers, and
      one or two letters usually representing the community of license, like K 47 SL (now KSFI, Salt Lake City, UT).

Click on the folder to see the authorizations that were contained in it:

Additional early FM licensed stations with FCC History Cards and FCC Facility ID Numbers, 1938 to 1947:

For more information on AM and FM radio broadcasting, please visit the Audio Division website, and the Broadcast Radio Links page.

For more information on Television broadcasting, please visit the Video Division website.

FCC > Media Bureau > Audio Division and Video Division, (202) 418-1600.