This thesis contributes to the literature seeking to understand the determinants and socioeconomic effects of cultural traits and family structure from a historical perspective. In Chapter 1, I investigate the relationship between intergenerational coresidence and mortality from Covid-19 in 2020. Using a cross-section of U.S. counties, I find a positive, significant, and robust association between intergenerational coresidence and Covid-19 mortality rates among the elderly. In Chapter 2, I delve into the complex historical interplay between fertility patterns and family structure in the United States. I document a new fact about the American fertility transition: women coresiding with their elderly parents had systematically lower fertility rates compared to those residing in nuclear families. This difference, although pronounced in earlier decades, diminishes over time. To rationalize this pattern, I construct a novel theoretical model incorporating endogenous fertility and family choices. The model posits that lower fertility rates in intergenerational families result from the lower allocation of resources to the younger generation compared to nuclear families. This resource allocation effect, driven by the interplay between the relative income of the young and their preferences for coresidence, is supported by dynamic general equilibrium simulations. In Chapter 3, I investigate the coexistence of social capital and individualism during the American frontier expansion. I leverage historical weather variability and the duration of the frontier expansion as plausibly exogenous variations influencing cooperative behavior and self-reliance, respectively. My findings reveal that in frontier counties experiencing higher weather variability, the return to individualism diminished, fostering larger religious communities—an early proxy for social capital. This chapter connects historical climate risk to prosocial behavior in individualism-prone environments, providing quantitative evidence for De Tocqueville’s doctrine of "self-interest rightly understood," where individual pursuits align with the common good.