By the 1960s, the music of Austrian composer Gustav Mahler had become an exceptionally--and enduringly--popular part of American concert life. But for much of the twentieth century, the place of Mahler's music in America's orchestral canon was passionately debated and not nearly so secure. This dissertation proposes that the growth of transatlantic modernism--in some ways a reaction to Mahler's Austro-German tradition--went hand in hand with the developing appreciation for Mahler's music in the United States between 1920 and 1960.