This dissertation introduces the concept of biological imagination, a new analytic framework for Jewish literary and cultural production in the United States. The Biological Imagination in Twentieth-Century Jewish American Culture argues that from the turn of the twentieth century to the present, Jewish American authors across genres repeatedly turn to themes and forms of biology—ranging from evolution to racial typology, to genetics—in order to locate Jewish inheritance in the body. While biological knowledge itself has been approached with understandable wariness since the Holocaust, due to its association with the race science that fueled the Nazi genocide, the dissertation illustrates that both in spite of, and because of, Jews’ vexed historical relationship to biology, Jewish American authors continue to infuse their works with biological knowledge after the historical chasm of 1945. That Jewish literary and cultural production should continue to incorporate, or obsess over, biological theories of inheritance, complicates the historical narrative of Jews in the United States as well as the way that Jewish American literature can be understood within American ethnic literature today.The biological imagination necessitates reexamination of the literary and cultural circulation of many of Jewish American culture’s central concerns, including language, immigration and assimilation, race and ethnicity, and gender and sexuality. Not only does biological knowledge enrapture fictional characters, but biological models of inheritance also deeply structure works’ narrative and poetic forms. Furthermore, this cultural phenomenon extends beyond literature, from photography in the 1910s, to contemporary television series. The dissertation assembles sources in English and in Yiddish, from the 1890s to the present, including The Rise of David Levinsky by Abraham Cahan, The Promised Land by Mary Antin, The Family Carnovsky by Israel Joshua Singer, Focus by Arthur Miller, Gentleman’s Agreement by Laura Z. Hobson, A Few Words in the Mother Tongue by Irena Klepfisz, Sources by Adrienne Rich, and Portnoy’s Complaint by Philip Roth, as well as the composite photography of Francis Galton and the Amazon series Transparent. More often evoking mystery than certainty, the biological imagination at once responds to and highlights the elusiveness of Jewish inheritance for Jewish authors in the United States.