Why do the callnames of all radio stations begin with 'K' or 'W'?!

Why do the callnames of all radio stations begin with 'K' or 'W'?

The station call names of every radio station I can think of becomes with "K" (ie KRTY) or "W" (ie. WKRP). What's the significance of this naming convention?

In the United States, the letters "W" and "K" were to be used.

At first, it didn't matter what part of the country a station was located in to use either letter.

Then, in 1923, The Federal Communications Commission ordained that all new radio stations east of the Mississippi River would use "W" as the first letter and stations west of the Mississippi would use "K".

Certain stations were "grandfathered" and allowed to keep their call letters for various reasons, even if they did not conform to the new edict.

By the way, Canadian stations begin with "C" and Mexican stations begin with "X"

the Bureau of Navigation, part of the U.S. Department of Commerce, began assigning three-letter call signs to American ships in early 1912, using the K prefix for ships on the Atlantic and Gulf coasts and W for ships on the Pacific coast and the Great Lakes; the reasons for choosing K and W, if any, are unknown. Shortly thereafter, at the London International Radiotelegraphic Convention, ranges of letters were assigned to each of the participating nations; in addition to W and most of the K range, the U.S. got the N prefix (to be used only by the navy).

On May 9, 1913, the U.S. Department of Commerce issued a 4-page document titled Radio Call Letters, which laid out the official policy in some detail. A couple of paragraphs bear particular mention:

3. (b) The combinations KDA to KZZ, with a few exceptions, are reserved for ship and coast stations on the Atlantic coast and Gulf of Mexico.
3. (c) The combinations beginning with W…are reserved, with a few exceptions, for ship and coast stations on the Pacific coast and the Great Lakes.

There you have it, clear as day: like the ships off the Atlantic coast, the land-based stations in the east were to have K designations, while stations in the west, like ships off the Pacific coast, were to have W designations. For entirely unknown reasons, though, these labels got swapped before they were implemented. Later that year, stations in the west began getting K call letters, while stations in the east got W call letters. A 1914 booklet of regulations titled Radio Stations of the United States codified the K-in-the-west, W-in-the-east practice, which was followed strictly thereafter, except when it wasn’t.