From their 1964 American debut to their much-lamented breakup in 1970, these mop-topped teen-idols-turned-cosmic-hipsters dominated the popular music scene and set new frontiers in music and society as a whole. While "I Want to Hold Your Hand" topped the charts at the beginning of 1964, the British Invasion really took off when the Fab Four arrived at New York's Kennedy Airport on February 7, 1964. Their two appearances on the "Ed Sullivan Show" drew a record 73 million viewers each. By April 1964 the Beatles had the top five best-selling singles and two best-selling albums in the U.S. - an unprecedented achievement in the popular-music industry. That domination continued throughout the '60s, even as the band's style and personality evolved. Among the hit singles on their 1966 album "Yesterday ... and Today" are "Yesterday," "Day Tripper," and "Drive My Car." Testament to the staying power of the Beatles' popularity, the hit single "Yesterday" still airs at least once every five minutes on American radio. It is also the most frequently covered song in rock-and-roll history.