This dissertation uses longitudinal micro-data from Stockholm between 1878 and 1926 to study the causes and consequences of the fertility transition and to examine the development of living standards inequality during industrialization. Although both processes have received much interest from researchers, we know relatively little of how either one played out among individuals in urban areas, which were both at the forefront of industrialization and the fertility decline. To address this deficiency, I have analyzed the development of socioeconomic differentials in fertility, children’s intergenerational social mobility, and infant and child mortality during Stockholm’s industrialization and fertility transition. The results of this work challenge many existing explanations of the fertility decline and reveal how, despite overall improvements in living standards, elite socioeconomic groups were able to continually leverage their superior resources to maintain significantly lower levels of infant and child mortality.