In early nineteenth-century Paris, a physician named Louis-René Villermé left his medical practice and began a research career. One of his landmark studies in Paris helps highlight the idea of ‘the City as a Field Site’ used in this chapter. Villermé was concerned with the controversies in his field at the time over whether disease was caused by contagion — the passage of illness from a sick to a healthy person through some yet unidentified process — or miasma. Miasma theory traced disease to the environment, broadly defined as filth, dirty air and noxious odours — commonly from rotting waste and dead bodies. Villermé was interested in investigating whether the environments of neighbourhoods including weather, altitude, proximity to the polluted Seine River, street width, housing density, trees and park space helped explain the distribution of mortality among populations in Paris (Porter, 1999, p. 68).