The purpose of this essay is to demonstrate the relevance of transnationalism to understanding historical European international migrations to the United States. The author attempts to do this in two ways. First, through analysis and critique of the historical literature, including his own past work, this essay demonstrates the ways in which a transnational framework might fill certain gaps in European immigration historiography. Second, the essay develops an example--letter-writing--of transnational activities in which migrants engaged during the nineteenth century, a part of the classic era of European immigration. It is the author's aim that readers will find in these discussions new frameworks that will deepen their understanding of international migration, and beyond that, of the similarity of international migration waves over time. The assumption of much of the research on today's international migrations is that these migrations and those of the historical past are so different in character that they cannot be understood using the same conceptual apparatus that historians have employed to study European migrations. There are indeed many differences, but, as Nancy Foner has ably demonstrated in a recent book, those differences are easily exaggerated. The author goes further to make a claim for the unity of American immigration history and historiography: not only do the three great migration waves of American history have much in common, but they can be productively studied using the same conceptual tools. By linking contemporary and historical migrations conceptually, and by finding unities in the experiences of old and new Americans, individuals may enrich the teaching of American history. (Contains 25 notes.)