West Side Story actually started out as East Side Story in Jerome Robbins' original pitch to Bernstein in 1947.

Srsly.

It set the Irish Catholic Jets against the Jewish Emeralds, which was in keeping with the ethnic make-up of the Lower East Side area of Manhattan. When they finally got around to making the film, gang conflict between whites and Puerto Ricans on the West Side was in the news.

So there you go.