Health concerns have directed urban planning in Africa south of Sahara since the nineteenth century. Modern epidemic prevention on the continent has its origin in the early twentieth century, when the spread of the third plague pandemic from Asia forced colonial governments in Africa to take precautions to prevent and control outbreaks of plague. During the first decades of the twentieth century, the threat of plague continued to direct town planning in colonial Africa, contributing to planning and building regulations that introduced racial segregation in urban areas as a sanitary measure. Already before, health concerns of the colonizers had directed town planning in colonial territories. Still, the experience of plague and the increased understanding of its epidemiology gave new impetus to planning solutions which emphasized sanitation and hygiene and prevented the free mingling of different racial groups in a colonial urban context. Dar es Salaam, saved from the plague pandemic, only followed this path in the 1920s when town planning solutions for plague prevention created an urban structure increasingly based on race. The paper is based on documentary analysis of published German and British colonial sources.