How do individuals’ social networks evolve throughout the life course? Are these network dynamics shaped by broader social structure? At an aggregate level, how has social capital changed in American society over the past half-century, and what are the implications for social inequality? This dissertation delves into these three questions over three chapters. Chapter one examines how pre-existing social disadvantage and contextual change are associated with changes in network size and structure in later life. I disentangle the between-individual and within-individual differences in these aspects using population-based egocentric network data. Shifting contextual factors are associated with changes in the network independent of the socioeconomic background. Pre-existing social disadvantage is associated with less favorable network characteristics. Chapter two investigates the long-term impact of criminal justice contact on close social circles. Even minor criminal justice contact could destabilize individuals’ close social circles. This study provides a new perspective on how mass incarceration has impacted the marginalized populations through networks. In the third chapter, I investigate how inequality in social capital has evolved with increasing income inequality in the U.S. I use 91 measures of social capital pooled from 23 U.S. surveys. The data suggests that the distribution in social capital is increasingly unequal across most dimensions of social capital. Collectively, these results indicate that social network inequality can reproduce and enlarge social inequality.