The author suggests that the American experience represents only one phase in a long history of global border crossing. She describes the relative normality of the pursuit of work across borders during the emergence of the European nation-states and explains the economic and political mass migrations of Italians and Eastern European Jews during the 19th and early 20th centuries. She also discusses the dislocations - particularly those after World War II - that have engendered the refugee concept. Using these examples, the author explores the causes of immigration that have resulted either in nations welcoming incomers as guests or disparaging them as aliens.