We are a new collaboration in the Spatial History Lab, working to map prostitution in Philadelphia in the nineteen teens using an array of unique primary sources and Geographic Information Systems (GIS) technology. We are creating a digital map of Philadelphia ca. 1915, to map a sample of approximately 1,000 Philadelphia police arrest records for disorderly street walking from 1912 to 1918. Sites of prostitution and other vice-related activities will be coupled with relevant contextual information such as ward boundaries, police districts, land uses, and military bases to reveal interesting patterns including ones in terms of nationality and race. Resulting visualizations will be used to develop and illustrate research findings for a chapter on prostitution in Michael Kahan’s book manuscript “Danger in the Streets: Physical Injury, Moral Hazards, and Urban Public Space, 1850-1920,” that traces the history of safety, danger and risk in city streets, from the introduction of horse-drawn streetcars to the rise of the automobile.