This study analyzes the geography of prostitution in twentieth-century Philadelphia. Specifically, it addresses how the spatial organization of the sex trade has changed over this time period and considers possible explanations for this change. The author evaluates the influence of market economics, police repression and moral stigmatization on prostitution’s geography in Philadelphia. The author relies on records of prostitution-related arrests, vice complaints, law enforcement testimony, press coverage, and governmental reports to determine the location of vice since the early 1900s. The author concludes that Philadelphia’s case study complicates the narrative of spatial change put forth by the existing scholarship, which argues that prostitution has dispersed over the twentieth century. Rather, Philadelphia' sex trade has consistently intensified in clusters or along packed corridors, while the location of these hubs has oscillated between the City’s downtown core and its peripheries. This geography has resulted from a dialectical process involving prostitutes’ own agency and the imposition of police repression.