Among the greatest accomplishments of the Second Industrial Revolution was to engender economic mobility–individuals’ abilities to improve their economic status over the course of their lives–par excellence in human history. This dissertation uses novel datasets and modern econometric methods to evaluate the potential, pathways, and possibilities offered by mobility. Because mobility is a phenomenon that unfolds over decades if not generations, the first two chapters leverage the tools of economic history. In Chapter 1, I use a natural experiment to study the long-run returns to promotions in the U.S. submarine service during the Second World War. In Chapter 2, I evaluate the welfare and political economic effects of the expansion of the Imperial German transport network. Yet the Second Industrial Revolution remains incomplete; in particular, mechanization is largely absent from Sub- Saharan African agriculture. Then, in Chapter 3, I conduct an inquiry into the adoption of maize shellers in Uganda.My first chapter studies the long-term consequences of an early career promotion. To answer this question with causal estimates, I study a natural experiment: the United States submarine force during the first half of the Second World War. When allocating promotions, the US Navy’s Bureau of Personnel endorsed enlisted men recommended by captains who had sunk enemy ships. Defects in the Mark 14 torpedo, however, meant that submarines were substantially less likely to sink ships, irrespective of crew quality, if the strength of the geomagnetic field in their patrol zone was too different than the historical field strength near Newport, Rhode Island. To identify exogenous variation in promotions, I construct a vector of instruments using quasi-random variation derived from submarine patrol locations. Leveraging a novel dataset linking enlisted men’s naval data to their later life outcomes, I find that conditional on surviving the war, promoted sailors lived 2.4 years longer than their non-promoted counterparts. Furthermore, exogenously promoted sailors lived in wealthier ZIP codes at the time of their deaths. These effects are pronounced for sailors who received submarine-success triggered promotions to the rate of chief petty officer, suggesting the importance of developing and exercising managerial ability for later life well-being. My second chapter, coauthored with Jacob Weber, evaluates the influence of Imperial Germany’s (1871 - 1918) infrastructure expansion on welfare and voter participation. Because rail and waterway construction in this period was largely motivated by military concerns, it constitutes a quasi-exogenous shock to trade exposure. Using a novel panel dataset synthesizing constituency-level data on voting, population, wages, and inter-constituency trade costs to discipline a canonical spatial equilibrium model, we find that infrastructure improvements raised welfare by 3-5%, mitigated migration from rural areas, and increased voter participation in national elections by about 0.25%. In my third chapter, coauthored with Livia Alfonsi, we investigate Ugandan smallholder farmers’ participation in rental markets for postharvest machinery; specifically, we study the adoption of the maize sheller. Traditional, human-powered methods of shelling maize are burdensome and lead to excess breakage of maize kernels. Using shellers saves time, reduces drudgery, and increases marketable quantities of maize. We provide case studies for two villages in the Eastern Region, where access to these machines and their requisite maintenance networks is relatively greater. We censused these villages to characterize the demand side of their rental markets; in particular, we estimated willingness to pay (WTP) among villagers through a Becker–DeGroot–Marschak-type (BDM) exercise. In providing policy recommendations to enable accelerated mechanization of postharvest processing machinery, we complement our case study evidence with a census of maize sheller rentiers from all four Ugandan regions. Together, the three chapters of my dissertation use rigorous research designs informed by economic theory to contribute toward the ongoing policy debate over enabling economic mobility in the 21st century.