Why is conceptualizing an American avant-garde particularly problematic? How productive is the term “avant-garde” for understanding the development of American modernism? As a concept, the “avant-garde” was defined almost entirely by theorists affiliated in various ways with the Frankfurt School using examples and with political expectations forged in western Europe. Various political and historical assumptions led to theories framing American modernist aesthetics as an impoverished variant of the European model. This chapter begins with a survey of some important theories of the avant-garde before considering the classic American modernist avant-garde – the years 1914–17 in Greenwich Village, New York City – as a case study, using poet William Carlos Williams as its touchstone. Evaluated from the perspective of European accounts, it suggests some limitations to the predominantly European framework of the avant-garde in illuminating American modernism with the example of another American poet: Hart Crane.