Sunday (July 4) marked the 40th anniversary of the first airing of "American Top 40" with Casey Kasem.

The National Association of Broadcasters Hall of Fame icon co-created the show that brought the Billboard Hot 100 into the homes of millions in audio form. Since, multiple generations of music fans have been introduced to following Billboard rankings, countless radio DJs have been inspired to enter the medium and artists have celebrated the honor of hearing Kasem pronounce their song "the biggest hit in the land."

"Here we go with the top 40 hits of the nation this week on 'American Top 40,' the best-selling and most-played songs from the Atlantic to the Pacific, from Canada to Mexico," Kasem said atop the program's first broadcast.

"This is Casey Kasem in Hollywood, and in the next three hours, we'll count down the 40 most popular hits in the United States this week, hot off the record charts of Billboard magazine for the week ending July 11, 1970."

While traversing the Hot 100's top 40 titles, Kasem would also incorporate other Billboard surveys, noting the No. 1 song each week on the country, dance and R&B charts.

Other features that grew into benchmarks included Kasem's running down of several of the affiliates airing "AT40," the host's signature stories detailing artist and song trivia and, most notably, the show's interactive "Long Distance Dedications."

No episode of "AT40" was complete without Kasem's trademark signoff: "Keep your feet on the ground, and keep reaching for the stars." The weekly farewell affirmation was spoken over the music that outlasted even the show's biggest No. 1 hits; the program's closing theme/jingle, "Shuckatoom," written by James R. Kirk and available only on pressings of "AT40," would fade into local programming, signifying a six-day and 20-hour wait until Kasem would return.