North America has a longer and richer history of transnational historiography than is commonly known. It could hardly have been otherwise for three nation states whose histories are so thoroughly entangled with each other and with global patterns of colonialism and imperialism. The most basic definition of transnational history is that it asks questions that transcend the boundaries of the nation-state. It has thus become a broad catch-all category that can include imperial, colonial, transoceanic, borderlands and comparative questions. As Benjamin Bryce and Alexander Freund wrote recently, transnational history does

not naively ignore or stubbornly deny the importance of national borders or nationalist ideologies, and the state and the nation continue to matter. However, this approach emphasizes experiences and processes below and above the national scale, and it can illustrate how local and regional histories can cross national borders. 1

The twentieth- and early twenty-first-century North American historiography that focuses on continental rather than imperial, colonial or transoceanic questions falls into two broad categories: a borderlands model that has dominated the writing about the U.S.–Mexico border and a comparative model that has dominated that of the U.S.–Canada border. Both can be traced as far back as the late nineteenth century, but they began to flourish in the 1920s as the post-WWI political climate encouraged North American scholars to reconsider the value of continental connections.