What are the names of the two rival street gangs in "West Side Story"?

When you're taking a play written in 1597 that's set in 14th-century Italy and trying to adapt it to fit 1950s New York, you'll need more than just some name changes to have the whole thing feel modern. In "Romeo and Juliet," neither the Capulets nor the Montagues know why they hate each other, but in "West Side Story," the Sharks and the Jets have a pretty good idea. Beyond all the twirls and fast-paced songs, the musical is about the real tensions of immigration and racism in mid-century America. Riff leads the Jets while Bernardo runs the Sharks, and when Tony (a former Jet) falls for Maria (Bernardo's sister), things get messy fast. Director Jerome Robbins took the gang rivalry so seriously during the Broadway production that he kept the actors playing Jets and Sharks separated, forbidding them from hanging out together and even making them rehearse in different rooms to build authentic tension. The tactic mostly worked, though Chita Rivera (a Shark) and dancer Tony Mordente (a Jet) fell in love anyway and got married. Just add that to the list of life imitating art.