Following the Spanish conquest of the 16^th century, Spanish American cities became centers of Spanish power and wealth but also formed a space where a multiracial society emerged out of the contact between Spaniards, Indians and Africans. In these urban centers, designed in a grid structure, residence correlated with economic and racial status. From Mexico City to Caracas to Buenos Aires, the grid's center was home to wealthy Spanish elites, while the outskirts were crowded by poor Indians and Africans. In this study, I show how residential patterns along the city grid reflected inequality in terms of class and race. At the same time, by analyzing geo-spatial data of various racial populations across time, I also present the social mobility, however limited, that was taking place in the 18^th century, as Indians, Africans, and racially-mixed people could move up the socioeconomic ladder despite formal-legal discrimination. This paper brings together questions in history, geography and sociology, addressing them by social scientific methods and GIS computerized analysis.