Call letter threads are lots of fun, but they sometimes end up getting pretty full of misinformation, too.
Fortunately, many of the legends and tall tales about early call letter assignments were debunked (or, in some cases, confirmed) authoritatively more than a decade ago, when Thomas White put out the first edition of his "Mystique of the Three-Letter Callsigns."
It's free for the reading right here:
http://earlyradiohistory.us/3myst.htm
A few of the key points White makes include:
*Requested three-letter callsigns: There were some, in the period after 1922 when three-letter calls were no longer being routinely assigned to new stations. WLS was requested, and yes it really does mean "World's Largest Store." WLW was not requested, and any "World's Largest Wireless" meaning was assigned later as PR puffery. There was a lot of PR puffery in early radio!
WGL was apparently a requested call in 1928, replacing the earlier WCWK ("Chester W. Keen"). The WGL calls had been used in Philadelphia and New York on unrelated stations.
*Calls were assigned from day one: It's true that there was no FRC until 1927, and no FCC until 1933, but the Department of Commerce was issuing licenses - and callsigns - almost from the start of broadcast radio. Only the very earliest ancestors of broadcast radio, stations like "San Jose Calling" (later KQW/KCBS), operated without calls. Everyone else had calls, and they were largely assigned sequentially in the first few years of broadcasting. White addresses some of the sequences in "Mystique," and others here:
http://earlyradiohistory.us/pion622l.htm
Of those first stations licensed up until June 1922, only two Indiana stations survived. WBAA was a sequential call assigned in April 1922, while WGAZ South Bend was sequential in June 1922, but later changed calls to the requested WSBT when that option became available.
And having thrown all that into the pot, let me add one callsign that I don't think has been mentioned yet in this thread: WIND stands not for the "WINDy city" of Chicago, but for "INDiana," since the station was originally licensed to Gary (and still transmits from NW Indiana.)