The Federal Communications Commission (FCC) assigns call signs to radio stations in the United States, and these call signs can start with any letter of the alphabet. However, there are more radio stations in the United States that start with the letter K than any other letter. This is because the FCC originally assigned call signs to radio stations based on their location. Radio stations in the western United States were assigned call signs that started with the letter K, while radio stations in the eastern United States were assigned call signs that started with the letter W. Over time, the FCC has relaxed these restrictions, and radio stations can now be assigned call signs that start with any letter of the alphabet.