This introductory chapter examines questions that have been raised about the evolving importance of the border, from whether global trade has made borders less relevant, to whether states still possess the capability (or the will) to control borders. A great deal has been written about border policies in Europe and the United States, but very little about how and why policies change, both over time and across space. In the United States, even during the most severe period of immigration restriction, borders were a minor focus of attention, and the northern and southern borders remained relatively open and only lightly patrolled. In Europe, even after the dismantling of the internal borders when the Schengen Agreement was implemented after 1995, the external borders still remained the responsibility of the member states, with relatively little coordination at the EU level. Therefore, why have borders become an important focus of politics?