Radio/TV call letters

Why do radio and tv station call letters start with “W” east of the Mississippi River, and “K” west?

We’re not sure.

(bolding mine)

Land stations were later given callsigns following ship practices, with K in the east and W in the west. Later, they defined a land boundary between K and W.

the USA is allowed to use call signs starting with AAA–ALZ, K, N, W; this is international treaty. W and K are used for broadcast TV and radio.

originally K was the west of Texas border line, later the Mississippi River. it was the convention used by the government from the start.

There are a number of exceptions, described in this essay.

And, yes, there are a few stations west of the Mississippi with call signs starting with W, and a few east of it with call signs starting with K, but they’re pretty much all very old stations that had their calls assigned before the convention was set in stone.

It is interesting, WSAJ, the first licensed land station, has the proper W for a Pennsylvania station. Second comer KDKA has a K

Why do U.S. radio call letters start with W in the east and K in the west (revisited)? in which Cecil abases and corrects himself.