This book examines the role played by statistics and cartography in defining the German national imaginary across the long nineteenth century. It asks how spatially specific knowledge about the nation was constructed, showing the contested and difficult nature of objectifying this frustratingly plastic substance. Here ideology and politics were not in and of themselves capable of providing satisfactory answers to questions about the geography and membership of the nation. Rather, technology also played a key role in this process, helping to produce the scientific authority needed to make such images believable. In this sense, the book is about how the abstract idea of the nation was transformed into a something that seemed practically discoverable and politically manageable. At the same time, however, the book also looks at the birth of radical nationalism in central Europe, advancing the novel argument that it was changes to the optics of seeing nationality rather than economic anxieties or ideological shifts that radicalized nationalist practice at the close of the nineteenth century. Numbers and maps enabled activists to “see” nationality in local and spatially specific ways, enabling them to make (and then evaluate) strategic decisions about where to best direct their resources. In essence, they transformed nationality into something that was actionable – a substance whose historical development could be shaped by the actions of ordinary people.