Bob Chaparro wrote:
Why Radio Was "Special" In The Early 20th Century
I've seen several photos of boxcars with banners proclaiming their load of radios. The reason was radio was something new and special in the early 20th Century.
In 1919, Frank Conrad, a Westinghouse engineer, began broadcasting music in Pittsburgh. These broadcasts stimulated the sales of crystal sets. The popularity of Conrad’s broadcasts led to Westinghouse establishing a radio station, KDKA, in 1920.
KDKA still exists (or did until quite recently), and was "grandfathered" in the general pattern of Western station call letters beginning with "K" and Eastern ones with "W".