At the opening of the twentieth century, Jewish scholars turned to archives as a primary source of Jewish history and culture, and created diverse archives of their own. It was to be, as one scholar put it, a "time to gather"--a time when Jews the world over worked to bring together the records of the Jewish past, but when the shared impulse to preserve the past led to intense conflict. This dissertation explores the landscape of twentieth-century Jewish archives, tracing a transnational network of archives and archivists in Germany, the United States, and Israel/Palestine. Rather than casting these archives as neutral oases of objectivity, this study examines them as highly political sites of struggle over control of Jewish culture and memory. It investigates Jews' rising interest in archives and the proliferation of archival projects that followed, and excavates a tradition of comprehensive collecting and the resulting conflicts over who could "own" the past. A Time to Gather argues that both before the Holocaust and especially in its aftermath, the act of creating Jewish archives was just as much about the future as it was about the past. In the twentieth century, Jews in various parts of the world harbored dreams of "total archives" that would comprehensively document Jewish life. These aspirations fueled fierce competition, as centralizing historical materials was one way to project cultural hegemony and to shape the way that history would be written. Against this backdrop, the study examines major archives including, among others, the Gesamtarchiv der deutschen Juden, founded in Berlin in 1905, the Jewish Historical General Archives in Jerusalem (since 1969 the Central Archives for the History of the Jewish People), and the American Jewish Archives in Cincinnati, both of which opened in 1947. This work seeks to comprehend the scope of this "time to gather," when Jewish scholars and leaders on three continents looked to archives as an important source of history and an anchor for communal memory, and to examine the significance of archiving for the development of the discipline of Jewish history as well as the politics of Jewish culture.