Dave Shrader wrote:
I'll stand to corrected but my recollection is that a further partition
existed within the USA in the 50s and earlier.

W was issued to stations, at least commercial stations, East of the
Mississippi and K was issued to station west of the Mississippi!!

For broadcast stations only.

In the very earliest days of radio, the dividing line was the eastern
borders of New Mexico/Colorado/Wyoming/Montana. They switched to the
Mississippi River in the 1920s.

http://www.earlyradiohistory.us/kwtrivia.htm
--
Doug Smith W9WI
Pleasant View (Nashville), TN EM66
http://www.w9wi.com