This book collects the main papers written by George Borjas on the economics of immigration during a decades-long career. Although there was little interest in immigration issues among economists before the 1980s, the literature has exploded since. The essays collected in this book represent some of the contributions that helped build the foundations of immigration economics. The essays cover a wide range of topics, including the assimilation of immigrants, the skill characteristics of the immigrant population, the intergenerational progress of immigrant households, the measurement of the impact of immigrants on the labor markets of receiving countries, and the calculation of the economic benefits from immigration. The essays included in this volume continue to be widely cited and have often set the research agenda for subsequent research on immigration in both receiving and sending countries.