American top 40 the most famous countdown show in radio history celebrate the 40th anniversary last week. As part of the special anniversary weekend, at40 host Ryan Seacrest commemorated the milestone with a tribute to the show’s creator and original host Casey Kasem. In addition to counting down the current top 40 songs, Seacrest revisited some of the greatest moments over the last four decades and recognized artists with amazing achievements in music.

"American top 40 is the soundtrack to life; it sparks emotion and memories, and has a huge impact on pop culture” stated Seacrest. "This show is really special to me. Not only because it’s the biggest countdown in the world, but because it’s the one show I grew up listening to as a kid, so I take a lot of pride in hosting the program every weekend."

The anniversary weekend also kicked off the "Lady Gaga Superfan Search." Seacrest asked listeners to prove they are Lady Gaga’s biggest fan by going to www.BING.com/Gaga and uploading a photo sporting their fiercest gaga fashion. The grand prize winner will be announced on July 23rd and will receive tickets to see lady gaga at lollapalooza in Chicago’s grant park (August 6-8); tickets to see lady gaga in Miami, New York and Las Vegas; as well as hotel accommodation and airfare to each of these shows.

American top 40 was created by Casey Kasem in 1970. Seacrest debuted as host of the program in January 2004.

AT40 Celebrates Forty Years

Interview with Ryan Seacrest