When I was in graduate school in the early 1990s I attended a conference on my campus. The auditorium was packed, the atmosphere charged. The topic was transnational migration and the deterritorialization of the nation-state. The speakers were prominent sociologists who were in the vanguard of a burgeoning scholarship about "globalization," a reference to a new interconnectedness in the world made possible by global capital, information technology, and the like. In this brave new world migrants lived in a social field that spanned borders, even oceans; they sent remittances back to relatives, they traveled back and forth, they were politically active in their home countries while living abroad… Of course, these were all familiar to the immigration historian—so what was new?

If these transnational social practices are not necessarily new, historians nevertheless owe a debt to the social scientists because they prompted us to look at history differently. Over the last dozen years or so, the "transnational turn" has arguably been the most important development in the historical discipline. Not least, it has challenged the long-held assumption that the nation is the basic unit of historical analysis. In doing so, transnational history has opened up new lines of research and produced historical knowledge that has revised all kinds of conventional understanding. There also have been consequences for the organization of the profession: Many departments have reorganized, or at least adjusted, their nation-based fields to accommodate these new modes of inquiry.

Broadly conceived, transnational history follows the movement or reach of peoples, ideas, and/or things across national (or other defined) borders. In addition, it involves empirical research in more than one nation's archives. Although "transnational" would seem, by definition, to refer to modern history (trans-national) the term has been also used to describe regional worlds of the pre- and early-modern periods (Atlantic world, Indian Ocean, medieval "Europe," and so on). I would not argue for any particular orthodoxy on this point, but the questions and stakes are different. For earlier periods, the concept perhaps simply renames already existing fields. For the modern period, however, fundamental categories are reframed and problematized. The nation is not effaced but is examined afresh—from different angles, from within and from without, in larger context, and in dynamic relation with myriad social forces, many of which cannot be contained by national boundaries.

Although transnational history is flourishing throughout the discipline, here I discuss histories that I am most familiar with, those that include U.S. history. In my own field of American immigration history transnational histories now abound. One would think that the field was natural ground for transnational study, but in fact there were many obstacles. In U.S. history, the "nation of immigrants" paradigm, with its themes of unidirectional movement, assimilation, and modernization, dominated academic and popular history since the mid-20th century. Other national historiographies, such as China and Mexico, held scant interest for those who had departed, viewing emigrants as either inconsequential or traitorous to the homeland. These barriers have largely given way, not least because of the increased economic and political role that diasporic communities play in sending countries. Transnational migration studies are about migration and much more; they are also about state formation and authority, the construction of borders, colonialism and imperialism, political economy, culture, and ideologies of gender, race, and development.1

Transnational study is not limited to migration history, of course. The field formerly known as U.S. diplomatic history has undergone a metamorphosis to become "America in the world." It is concerned with themes far broader than state relations and based on research in archives outside the U.S., showing how different America's position and relations in the world looks when examined from the outside or from below.2 Cultural and intellectual histories have also been transformed by transnational research. Recent works have shown, for example, how trans-Atlantic and trans-Pacific commerce in commodities (porcelain, tea, furs, cotton) and ideas (liberalism, racism, law) shaped national identities.3

The transnational spirit has also breathed new life into comparative history and enabled it to rise above nationalist historiography. The new comparative histories do not use one case to privilege or validate another. Rather, they use comparison to show local political contingencies of broader global phenomena, whether slave emancipation, the dispossession of indigenous people by settler colonials, or the inclusion of racial and colonial others as citizens and soldiers.4

At its best, transnational history rethinks not just national history but also challenges nationalist history. If the disciplinary convention takes the nation as the assumed object of history, a more pernicious legacy lurks beneath, the nation as subject or, as Hegel would have it, the Nation as History. The greatest stakes lay here, in my view. For as much as we have all foresworn teleological history, nationalism remains a powerful influence upon the writing of history. The idea of some unique "greatness," fulfilled by linear history, remains at the core of every nation's story of itself. That story is reiterated in the popular media, in schoolbooks, in museum exhibits, and in the speeches of elected officials, and it is still present in academic history, even if in more subtle expression.

Transnational history offers an opportunity to alter the master narratives of national histories. This was also the task of the two last great turns in the discipline, social history and poststructuralism, which both focused their attack by concentrating on the dynamics of power (albeit in different ways). Of course, we must continue to write histories about oppression and subordination, as well as resistance and opposition; but this is not an uncomplicated endeavor. In the United States, one measure of social history's success has been the mainstreaming of multiculturalism; yet nationalism has cunningly co-opted social history's success to vindicate the exceptionalism of American democratic inclusion.

If social history rewrote history from the bottom up, transnational history proceeds from the outside in. By directing attention to the circuits and flows of social forces and discourses that span nations and cultures, we unfasten the blinders of national history. In a sense it is an indirect approach, which hopes by way of the broader context to deflate claims of national greatness and to gesture to histories that are more connected, more aware and of a piece with the modern world.

As with all historiographic turns, there is the danger of excess. Transnational history should not mean an end to nation-specific histories, for the nation exists historically, and it remains the principal unit of domestic politics. But transnationalism asks—and especially of American historians, who carry the burden of the exceptionalist tradition—that we situate the nation in a global context and that we view our place in the world as the moral equals with all others.

Here I wish to point out another danger, especially for those of us who are Americanists and Europeanists. We must be conscious that, owing to our privileged position in the world and within the global academy, we run the risk of turning transnational history into another variant of imperial history. "North American" history cannot be that which remains centered in the United States, with Canada and Mexico appended thereto. British history may be enjoying a revival with the study of empire, but without mastery of the historiographies, languages, and archives of, say, India or Egypt, we may hesitate to say it is transnational history. As someone who is studying Chinese diasporic labor in the 19th-century Pacific world, I remain daunted and humbled by the research demands that I face. But the rewards are potentially great, so I push on.

Mae Ngai is professor of history at Columbia University. She is the author of several books on immigrants, including, most recently, The Lucky Ones: One Family and the Extraordinary Invention of Chinese America and Impossible Subjects: Illegal Aliens and the Making of Modern America.

Notes

1. The examples cited in these notes are just a small sample of notable work. Madeline Hsu, Dreaming of Gold, Dreaming of Home: Transnationalism and Migration between the United States and South China (Stanford: Stanford University Press, 2000); Eiichiro Azuma, Between Two Empires: Race, History, and Transnationalism in Japanese America (New York: Oxford University Press, 2005); Jesse Huffnung-Garskoff, A Tale of Two Cities: New York and Santo Domingo since 1950 (Princeton, 2008); Deborah Cohen, Braceros: Migrant Citizens and Transnational Subjects in the Postwar United States and Mexico (Chapel Hill: University of North Carolina Press, 2011); Kornel Chang, Pacific Connections: The Making of the U.S.-Canadian Borderlands (Berkeley: University of California Press, 2012).

2. Mark Bradley, Imagining Vietnam and America: The Making of Postcolonial Vietnam (Chapel Hill: University of North California Press, 2000); Erez Manela, The Wilsonian Moment: Self-Determination and the International Origins of Nationalist Anti-Colonialism (New York: Oxford University Press, 2007). A particularly interesting angle is with African American history. See Penny Von Eschen, Satchmo Blows up the World: Jazz Ambassadors Play the Cold War (Cambridge, MA: Harvard University Press, 2005); Andrew Zimmerman, Alabama in Africa: Booker T. Washington, German Empire, and the Globalization of the New South (Princeton: Princeton University Press, 2010).

3. Kariann Yokota, Unbecoming British: How Revolutionary America became a Postcolonial Nation (New York: Oxford University Press, 2011); Marilyn Lake and Henry Reynolds, Drawing the Global Color Line: White Men's Countries and the International Challenge of Racial Equality (London, UK: Cambridge University Press, 2008); Christopher Tomlins, Freedom Bound: Labor, Law and Civic Identity in Colonizing English America (New York: Cambridge University Press, 2010).

4. Rebecca Scott, Degrees of Freedom: Louisiana and Cuba after Slavery (Cambridge, MA: Harvard University Press, 2008); Lisa Ford, Settler Sovereignty: Jurisdiction and Indigenous People in America and Australia (Cambridge, MA: Harvard University Press, 2010); T. Fujitani, Race for Empire: Koreans as Japanese and Japanese as Americans during World War II (Berkeley: University of California Press, 2011).