Book section: In the last decades of the nineteenth century, industrialized countries saw their urban mortality fall and the end to the rural-urban mortality differentials, once vastly favourable to rural areas. This process can be linked with two broad phenomena: a rise in income and improved sanitation. Here we focus on income and take advantage of the unusual quantity, quality, and variety of statistics computed by the statistical department of the Paris municipality from 1880 to 1914. The difference between the best and worst neighbourhoods (quartiers) in Paris in life expectancy is over 10 years in life expectancy. To explain such huge mortality differentials between neighbourhoods, we add information on income and wealth from fiscal records, the distribution on rental values for each neighbourhood. We document that the disparities in mortality between neighbourhoods were strongly related these income indicators. Over time, mortality fell partly because income increases and partly because of a change of the mortality income relationship.