This paper investigates a common mode of visual communication in planning practice, the use of maps to regulate urban development. Holding equal legal status with the text, the zoning map was invented in the early twentieth century as a tool for implementing municipal policy and, although debated, modified, and sometimes repurposed over the past nine decades, it remains standard. Mundane and largely taken for granted, the zoning map itself has aroused little scholarly interest. However, as an image of the city and as a graphic intermediary used in administrative processes, it reveals how planning thought is embedded in planning tools.