West Side Story is a musical written by Arthur Laurents (book), Leonard Bernstein (music), and Stephen Sondheim (lyrics). The story is based loosely on Shakespeare's Romeo and Juliet, which was, in turn, based on a narrative poem by Arthur Brooke entitled The Tragicall Historye of Romeus and Juliet (1562). Set on Manhattan's Upper West Side, the musical explores the rivalry between two teenage gangs of different ethnic and cultural backgrounds. The young protagonist, Anton ("Tony"), who belongs to the white gang, falls in love with Maria, the sister of the leader of the rival Puerto Rican gang. The dark theme, sophisticated music, extended dance scenes, and focus on social problems marked a turning point in American musical theater. Bernstein's score for the musical has become extremely popular; it includes "Something's Coming", "Maria", "America," "Somewhere," "Tonight", "Jet Song", "I Feel Pretty", "On