Louis Bernstein (August 25, 1918 – October 14, 1990), professionally known as Leonard Bernstein, was an American composer, conductor, pianist, and educator. He became the first American-born conductor to achieve international acclaim, serving as Music Director of the New York Philharmonic from 1958 to 1969. Bernstein composed the music for West Side Story (1957), one of the most celebrated musicals in history, as well as works including Candide (1956), On the Town (1944), and Mass (1971). Renowned for his contributions to both classical music and musical theatre, he remains one of the most influential musicians of the twentieth century.