Set in the mid-1950s in the Upper West Side of Manhattan in New York City, then a multiracial, blue-collar neighborhood. The musical explores the rivalry between the Jets and the Sharks, two teenage street gangs of different ethnic backgrounds. The Sharks, who are recent migrants from Puerto Rico, and the Jets, who are white, vie for dominance of the neighborhood, and the police try to keep order. The young protagonist, Tony, a former member of the Jets and best friend of the gang’s leader, Riff, falls in love with Maria, the sister of Bernardo, the leader of the Sharks. The dark theme, sophisticated music, extended dance scenes, tragic love story, and focus on social problems marked a turning point in musical theatre.