The slave market in Rio de Janeiro was transformed over the course of the nineteenth century. Prior to 1850, slaves poured into the city from Africa via the Atlantic trade. Buying and selling slaves then shifted to a local market typified by individual sales. Rather than a concentrated process dominated by formal market spaces and professional slave traders, the slave market in Rio de Janeiro was, by 1869, a continuous process that encompassed every neighborhood in the city. Mapping the origins, destinations, and characteristics of slaves, using detailed transaction data from 1869, highlights the ubiquity of slavery in Rio de Janeiro and the movement of slaves into new environments.