When the French Jewish composer Darius Milhaud (1892–1974) fled his homeland with his wife and son at the time of the German invasion in 1940, this displacement marked the beginning of three decades of engagement with the musical culture and institutions of the United States. After seven years of wartime exile in Oakland, California, Darius and Madeleine Milhaud divided their time between Oakland and Paris, taking on a transatlantic existence that enabled them to assume distinct roles in U.S. musical life. Both during and after World War II, the composer taught on the faculty of Mills College, participated in intersecting musical networks, and continued to compose prolifically. He also continually renegotiated his identity as a composer—and as a Frenchman in the United States—in response to professional opportunities, personal circumstances, and cultural shifts. This dissertation presents the first in-depth study of Milhaud’s activity in the United States, interpreting the results of new archival research through frameworks of identity construction and transnational mobility. In exile, Milhaud emphasized Frenchness to create space for himself in the U.S. musical landscape while also “defending French culture” through music. After the war, he continued to present himself as a “French composer,” while Jewish identity also took on an increasingly prominent place in his professional life as new institutions and ideologies of “Jewish music” emerged. Milhaud established a reputation as an aesthetically open-minded teacher, and when his neoclassical idiom began to fall out of favor, he attempted to exert continued authority by positioning himself as a mediator between the musical establishment and the new avant-garde, connected to U.S. and French musical communities through his yearly travels. During this time, Madeleine Milhaud carried out her own creative activity, but also oriented her public image around that of her husband, whose postwar reputation was complicated by factors including age and disability. Through an exploration of one composer’s construction of identity, this dissertation asks questions about the goals and effects of musical biography while contributing to scholarly conversations on exile and migration, French and Jewish identities, and the generational shifts of postwar modernism.