From the WSJ:
Arthur Laurents needed a Maria for his upcoming Broadway revival of "West Side Story." The 91-year-old director, who wrote the libretto for the legendary 1957 musical, found her on YouTube.
Josefina Scaglione was an Argentine stage actress working in Buenos Aires. She spoke English with a rich Spanish accent, was unknown to American audiences and was exactly what Mr. Laurents had been searching for.
Read the whole thing. Here she is with Libertango: