Few would argue the premise that Leonard Bernstein’s music sounds prototypically American. Most of his works include numerous passages that would only have been written by someone from the United States, especially one active from the 1940s to the 1980s. His frequent cultivation of musical tropes associated with various types of jazz, blues, Tin Pan Alley, rock, Latin music, and concert music by the likes of Aaron Copland help make Bernstein’s interest in an American sound perhaps the single most significant factor that defines his musical style. This chapter considers how that style developed in terms of when and how he discovered and incorporated major American musical styles. The musical influences blend with other inspirations from Jewish music and Western concert music to render Bernstein one of the most eclectic composers of his generation.