A substantial body of literature has examined the roles of physical and human capital in shaping development outcomes such as economic growth, governance, and innovation. However, comparatively less attention has been paid to social capital and its broader societal implications. This study explores the relationship between social capital and protest mobilization in the United States, arguing that social capital plays a critical role not only in fostering cooperation and development but also in shaping patterns of collective dissent. Social capital, commonly understood as networks of trust, shared values, and civic engagement, facilitates coordinated action and supports institutional stability. Yet, its erosion can produce significant social and political consequences. Drawing on existing theoretical and empirical insights, this paper contends that increasing social and economic inequalities undermine shared values and weaken trust among individuals and between citizens and institutions. Such breakdowns in social cohesion create fertile ground for protest movements as marginalized groups seek to articulate grievances and demand change. The rise of diverse protest movements in the United States—including those related to racial justice, gender equality, LGBTQ+ rights, gun control, immigration, anti-corruption, and environmental concerns—reflects deeper fractures in the social fabric. The study highlights the dual nature of social capital: while strong social ties can promote stability and cooperation, their fragmentation can equally facilitate mobilization and collective action. By linking social capital to protest dynamics, this research contributes to a more nuanced understanding of how social structures influence political behavior. Ultimately, the paper underscores the importance of rebuilding trust, promoting inclusivity, and addressing structural inequalities to strengthen social cohesion and mitigate conflict.