What does the “W” at the start of U.S. radio stations’ call signs typically indicate?

All radio stations today have a four-letter identification code, or call sign. The station owners may come up with a “catchier” name than just the four letters, but you can still hear the call sign sprinkled in with your morning news. When, how, and why did this come about?

Call signs serve to identify individual radio and television stations. Most U.S. call signs are issued by the Federal Communications Commission (FCC). The majority of U.S. stations have a call sign that starts with either K or W.

The acronyms were created in 1912, when an international conference agreed that different call letters should be assigned to different countries, for the purpose of TV and radio signal identification. There was a valid reason: lack of coordination and a duplication of call signs used by merchant ships were proving to be a threat to maritime navigation. (Prior to the adoption of the Radio Act of 1912, the U.S did not require stations to be licensed at all.) The letters assigned for use in the U.S. were W, K, N, and A.

Of those, N and A are primarily used to identify military stations. Radio and TV stations east of the Mississippi were assigned W, and those west of the Mississippi were assigned K. In the past, prefixes beginning with "A" were assigned to U.S. Army stations and prefixes beginning with "N" to U.S. Navy stations.

There are exceptions; however, if your favorite radio station has a “W” at the beginning, odds are it’s east of the Mississippi.