On July 4, 1970, the countdown started. Originally hosted by Casey Kasem, American Top 40 played "the best selling and most-played songs from the Atlantic to the Pacific, from Canada to Mexico," as he stated on the first program broadcast 50 years ago as of tomorrow.
On any given week, American Top 40 could feature a ballad, next to a country song, next to a funk song, next to a rock song. The show became a national obsession but 50 years ago, it was considered a risky idea.