Book excerpt: This book embraces an emerging paradox of human geography: the growth of cities along international boundaries. For many years the world system was ordered in such a way that international boundaries remained essentially free of human settlement. In the last three decades, however, the axioms of traditional geopolitical organization have been shattered; in a number of areas in the world, including the United States-Mexico, United States-Canada, and western European border regions, boundaries have come to house large-scale cities. -- From Preface (page xi).