From the colonial era of waterborne transport, through nineteenth-century changes in transportation and communication, to globalization, the history of the Great Lakes Basin has been shaped by the people, goods, and capital crossing and recrossing the U.S.-Canadian border. During the past three centuries, the region has been buffeted by efforts to benefit from or defeat economic and political integration and by the politics of imposing, tightening, or relaxing the bisecting international border. Where tariff policy was used in the early national period to open the border for agricultural goods, growing protectionism in both countries transformed the border into a bulwark against foreign competition after the 1860s. In the twentieth century, labour migration, followed by multinational corporations, fundamentally altered the customary pairing of capital and nation to that of capital versus nation, challenging the concept of international borders as key factors in national development. In tracing the economic development of the Great Lakes Basin as borderland and as transnational region, the authors of Permeable Border : The Great Lakes Basin as Transnational Region, 1650-1990 have provided a regional history that transcends national borders and makes vital connections between two national histories that are too often studied as wholly separate.