The roots of the first British Invasion were sown with the explosion of American Rock and Roll in 1955. Following the successful export of Bill Haley and the Comets , Elvis Presley , and other rock 'n' roll acts in the late 1950s , large numbers of British teens formed bands to emulate their American heroes. They copied both the musical styles and the rebellious images of the Americans, both of which deeply resonated with UK youth at the time. Britain produced a few successful homegrown artists during this time, such as Cliff Richard and The Shadows . But their impact on US and world record charts was limited, with only a handful of #1 recordings (such as The Tornadoes (with Telstar) and Acker Bilk with Stranger on the Shore, both instrumentals .

The meteoric breakout of The Beatles in the UK market in early 1963 proved to be the catalyst for the explosion. Their unprecedented success galvanized and stimulated their peers and the UK music industry as a whole, and paved the way for the imminent eruption of UK artists into the US and world markets. I Want to Hold Your Hand zoomed to the top of the USA charts just as The Beatles came to America for the first time. Their historic appearance on The Ed Sullivan Show on February 9 , 1964 was watched by what was then the largest television audience in history. This appearance was a remarkable social and cultural milestone of the 1960's, and marked the dramatic start of the British Invasion.

The Beatles' two year backlog of hit songs from England quickly came to dominate the American charts, and on April 4 of that year they occupied the top five spots on the Billboard magazine Hot 100 music survey, a feat unmatched before or since. Their success opened the floodgates for other British acts to market their music in the United States, beginning with The Dave Clark Five . They were quickly followed (in rough chronological order of US chart success) by Gerry and the Pacemakers , Peter and Gordon , The Animals , The Kinks , Manfred Mann , Herman's Hermits , the Rolling Stones , The Yardbirds , The Zombies , and Petula Clark by the end of 1964.
(From Wikipedia)