In antebellum New Orleans, the increased frequency and virulence of yellow fever was not a simple consequence of the Atlantic slave trade. The growth of large-scale sugar production and the consequent growth of the city as an urban port necessitated major changes to regional landscape and water system, which facilitated the growth of the city’s <i>Aedes aegypti</i> mosquito population. Meanwhile, the growth of the urban human population, which included a large proportion of newcomers who had not previously been exposed to yellow fever, provided a host population that enabled the virus to thrive.