Q & A: The Mystery of K and W Call Letters

I get a lot of e-mails from people asking me about television shows, made-for-TV movies or miniseries they remember from years or decades past. I try to answer each question as best I can. Every now and then I like to dig through my inbox and pull out a few choice e-mails to answer here at Television Obscurities for everyone to read. Keep reading for today’s questions and answers.

I’ve asked the following question for years, and never got a good answer: Why do stations east of the Mississippi generally start with W, and west of the Mississippi start with K? I’ve heard something about early transmitters from Westinghouse and Kaiser, but nothing definitive. Any ideas? Thanks.

The reason you haven’t been able to find a good, definitive answer is likely due to the fact that there doesn’t appear to be a good, definitive answer why certain stations were given call letters starting with K and others with W. Thomas H. White has written some wonderful articles for United States Early Radio History about the history of radio call letters. In “Mystique of the Three-Letter Callsigns” he notes that when the United States signed a 1912 radio regulatory act (I believe this was the Berlin International Radiotelegraph Conference) “call letter assignments became formalized under federal authority. Under international agreement unique initial letters were allotted among the various nations.”

He quotes from a 1914 government document (the full text of which is available here) describing the call letters available for stations in the United States and then writes the following:

Notice the policy was that calls for ocean-going ship stations started with a different letter than the land stations they communicated with: in the West ships received W– calls and land stations were assigned K–, while the reverse was true in the East, with K– ship calls and W– land calls. (NOTE: The assignment of W and K to the United States appears to have been completely arbitrary–the letters have no particular significance. N, however, had been commonly used by the U.S. Navy since November, 1909).

Later in the article, White explains that in 1923 the Mississippi River was chosen as the dividing line between newly licensed “W” stations and “K” stations, with existing stations allowed to keep their current call signs. Another article, “K/W Call Letters in the United States,” focuses on the various stations that don’t (or didn’t) fall into the K/W divide.

A December 1940 article in The New York Times discussing “a new system of call letters” adopted by the FCC explained that “under international agreement, the first call letters will be N for the use of the Navy and Coast Guard, K for stations west of the Mississippi and the Territories and W for stations east of the Mississippi” [1]. Another article, this one published in December of 1946, wrote that “until the FCC came into existence in the 1934, there were only two restrictions on a station’s choice of call letters: they should not number more than than three or four, and the first letter was supposed to be W (for stations east of the Mississippi) or K (for stations west)” [2].

So, to sum up, nobody seems to know why the decision was made to assign the letters W and K to the United States. And there doesn’t seem to be any rationale behind giving stations in one part of the country “W” call letters and others “K” letters. But ever since 1923, when the Mississippi River was made the boundary, people have been wondering why. If there is a good, definitive answer, please let me know.

Works Cited:

1 “FM Licenses Given Seven Radio Stations.” New York Times. 8 Dec. 1940: 63.
2 Rosenmayer, Warren R. “Letters in the Air.” New York Times. 8 Dec. 1946: 161.


  • Cee Jay says:

    There are exceptions to this rule however, KYW in Philadelphia was the NBC station for years and is now a CBS station and KDKA in Pittsburgh also a CSB station…got the information from Wikipedia

  • Barry I. Grauman says:

    Yes, ans they’re the ONLY TV stations East of the Rockies that carry a “K” in their call letters…

  • OM says:

    …A couple of points:

    1) Callsigns starting with “N” were, for a number of years, assigned to Novice-class license holders in the US Amateur “Ham” Radio Service until, IIRC, the late 1980s. There was talk about phasing them out in the 1970s as well.

    2) The reason for the split being the Mississippi River is that, even today, it’s considered the “geographical divide” between the East and West sections of the continental US. In those days when radio wasn’t 100% understood, the K/W distinction assisted in determining the source of radio signals with regards to propagation or “skip”. If sunspot activity had saturated the “D”, “E” and “Sporadic F” layers of the ionosphere, it was possible for a thousand-watt signal to not be heard across down, but would blow your doors off a thousand miles away. At the same time, such AM “skipland” signals could be so distorted by the ionosphere that about the only thing you had a chance of picking up and understanding was the callsign at the top of the hour. If all you got was the “K” or the “W”, then at least someone in a market getting saturated with someone else’s signal would be able to begin to deduce who was broadcasting the signal and/or bleedover.

    Or, to sum it up a little: the division occurred to assist location and triangulation of radio signals across a continent in a time when such techniques were new and problematic.

    3) One callsign plan that was dropped before it was implemented was for the 2nd letter of the callsign to represent the state in which the station was located. This was never put in place for unspecified reasons, but some FCC historians believe it was nixed for the same reasons that callsigns went from 3 letters to 4; to assist in broadcasters being able to request callsigns that reflected their specific marketing “personalities”.

    4) Stations with “K” callsigns east of the Mississippi and “W” west of it received their callsigns because the station went on the air *before* the FCC finalized the callsign rules. IN this region, WOAI is probably the best, oldest example, in that both the AM and TV stations retained a callsign that one would expect for an Eastern station.

    5) The US has a range of callsigns that it actually does not use even though it’s been assign them since the Berlin Accords: AAAA-AZZZ. Note that while the FAA uses this range for assigning airplane registration numbers, and the number can be used as a callsign or location marker signal, such use is *not* considered the same as a broadcast callsign.

  • OM says:

    …One other side note about the use of “K” and “W” in callsigns: when the CB Radio boom hit in the latter half of the 1970’s, the FCC came *very* close to issuing CB licenses using “W” as well as the already-in-use “K”. The reason had nothing to do with geography, but with the demand for licenses threatening to exceed the number of licenses available in the range KAA-0001 to KZZ-9999. The FCC instead chose to simply add an extra letter to the prefix, thus increasing the number of licenses available by an order of magnitude.

    Not that this ever got tested. The FCC eventually gave up on attempting to regulate the 11M band after the CB craze died out, and made it a license-free band…

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