In this chapter we discuss the data sources and methods available for studying the spatial distribution of economic activity in North America. We document facts about the specialization of states and regions, as well as locations differentiated by their degree of urbanization. We also report characteristics of the industries in which locations specialize. For example, establishment size and materials intensity are shown to vary in systematic ways with regional specialization. With these facts as a backdrop, we begin to consider the question, Why do locations specialize as they do?