A series of deadly epidemics of yellow fever ravaged Philadelphia and other eastern seaboard cities of the United States in the 1790s. Although medical opinion failed to reach consensus on the causes of the outbreaks, the events substantially influenced American thinking about the benevolence and improvability of the national climate. The belief that climate was being civilized by extending cultivation across the continent gave way to a concern with improving the quality of air in specific urban locations. Measures to enhance urban sanitation arose from the debate over the American “atmospheric constitution” that was stimulated by the yellow fever epidemics.
