Anthropology is inseparable from writing, whether in field diaries, letters, articles, or books. Among these writings, letters form paper bridges—holding a special place as material artifacts uniquely capable of building scholarly communities and sustaining relationships with field collaborators long after the fieldwork is completed. The story of Franz Boas, one of the founders of American anthropology, can be imagined as a res publica literaria, a network that, like its Renaissance prototype, shaped the contours of transnational anthropology. This two-part volume chronicles more than forty years of Boas's collaborations and friendships with Russian and Soviet anthropologists, following a small group of anthropologists as they built the house of Arctic and Siberian anthropology. Through these letters, readers are introduced to a lesser-known aspect of Boas's political life and his ambition to redefine anthropology as a transnational discipline, one that transcended national borders and political obstacles. Through meticulously gathered correspondence from more than thirty archives in the United States, Russia, France, and Norway, The Franz Boas Papers, Volume 3 reveals an untold chapter in the history of anthropology.