Brian Wilson was the JS Bach of the pop song; the way he arranged harmonies, devised "pure and easy" melodies, and used found sounds became an instruction manual for an entire generation on how to write pop symphonies.
Also worth noting that the Beach Boys were the first pop band to evoke an era-specific vision of Southern California, later on followed by bands like the Doors, Eagles, Steely Dan, X, Guns and Roses, and the Red Hot Chili Peppers.
It can be argued that the influence of the Beach Boys (like Scott Walker) was much stronger in the UK than in the States. You have the Beatles and Who, but you also have newer bands like the Jesus and Mary Chain and Spiritualized.
Directory of Tennis Warehouse Clubs (courtesy of Mountain Ghost)