The show debuted on seven stations but soon went nationwide. In October 1978, the show expanded from three hours to four. "American Top 40" success spawned several imitators, including a weekly half-hour music video television show, "America's Top 10", hosted by Kasem himself. "When we first went on the air, I thought we would be around for at least 20 years," he later remarked. "I knew the formula worked. I knew people tuned in to find out what the number 1 record was." Because of his great knowledge of music, Kasem became known as not just a disc jockey, but also a music historian.