what's the 'K' in KUOW?

I am a huge fun of radio, but I have always wondered about where does the name of each radio station comes from. What does the starting letter 'K' stands for.

So I finally broke down and looked it up. According to this wiki entry, the rules for the radio station names ( or "calling signs" as they call it) goes:

In the United States, broadcast stations have call signs between three and six characters in length, though the minimum length for new stations is four letters. An additional suffix may also be added, indicating a specific broadcast service type. Full-power stations receive four-letter call signs, while broadcast translator stations usually receive call signs with five or six characters, including two or three numbers. Generally, call signs begin with "K" west of the Mississippi River, and "W" to the east.