This book focusses on the instruments, practices, and materialities produced by various authorities to monitor, regulate, and identify migrants in European cities from the sixteenth to the twentieth centuries. Whereas research on migration regulation typically looks at local policies for the early modern period and at state policies for the contemporary period, this book avoids the stalemate of modernity narratives by exploring a long-term genealogy of migration regulation in which cities played a pivotal role. The case studies range from early modern Venice, Stockholm and Constantinople, to nineteenth- and twentieth-century port towns and capital cities such as London and Vienna.