July 4, 1970: the internationally-syndicated radio countdown show American Top 40 launched. The show counted down the biggest hits in the U.S., starting with #40 and working its way to #1. The Billboard Hot 100 charts, widely considered the industry standard, were the original source material. In the early ‘90s, they based the list off the Hot 100 Airplay chart and later the Top 40 Mainstream chart. When Kasem returned in 1998, AT40 switched to Radio and Records. In 2000, Mediabase began providing the data. Those charts are currently published on Tuesdays in USA Today.
Casey Kasem was the show’s original DJ and a co-creator. He is most associated with the show, having hosted it from its inception through 1988. Shadoe Stevens hosted from 1988-1995 and then the show went on hiatus for three years. Kasem returned in 1998, hosting until 2004. Ryan Seacrest has hosted it since then.
AT40 started as a three-hour show, expanding to four hours in 1978. By the early ‘80s, the show was available in 520 stations in the United States and in 50 countries around the world.
The inaugural show aired on seven radio stations. Three Dog Night’s “Mama Told Me Not to Come” was the first #1. Both Elvis Presley and The Beatles were in the top 10.
Kasem put his stamp on the show in several ways, most notably through long distance dedications. Listeners wrote letters with emotional personal stories and requested a song. Kasem read the letter on-air and then played the song. He was also well known for his signature closing motto: “Keep your feet on the ground and keep reaching for the stars.”
- Wikipedia entry on American Top 40
- official American Top 40 site
- About.com: What Does Top 40 Mean? by Bill Lamb