Statistics, generated by censuses, represent knowledge of society and environment used in the government of complex hierarchical societies. In this article we discuss the changing ways that censuses have reflected and constructed corporeal and cultural difference in Mexico. We show that shifts in conceptualizing and identifying racial and ethnic groups in Mexico are associated with larger social dynamics, and our history of these determinations is organized according to a series of periods—colonial, mercantile; Porfirian; revolutionary; and neoliberal—that chart changes in political economy as well as shifts in census categories and statistical tools. Second, we point out a shift in the representational technologies of statistics from encyclopedic forms to enumerative forms that occurred in Mexico in the last decades of the nineteenth century. We trace categories of difference across the transition from encyclopedic to enumerative statistics and also describe a shifting balance in the content of those categories among linguistic, cultural and corporeal qualities.