I use data for consistently defined municipalities to describe spatial patterns in population growth in Puerto Rico across all stages of economic development and rule by Spain and then the United States. The spatial distribution of population began to resemble the modern distribution after the turn of the twentieth century, around the time that municipal population densities diverged. Municipal population growth was positively correlated with crop production in the preindustrial era and was negatively correlated with agricultural employment from 1899 to 1970. Urbanization commenced around 1900, decades earlier than generally believed and before most of the Caribbean and Central America.