This project focuses on grassroots peacebuilding efforts across 182 rural villages in Eastern Antioquia, Colombia. For nearly a decade, these villages were caught on the frontlines of the civil conflict between the Revolutionary Armed Forces of Colombia (FARC), the National Liberation Army (ELN), paramilitary groups, and Colombian state forces. Despite their proximity, villages experienced different types of armed occupation and violence wielded against civilians. Since the conflict subsided in this region, villages have also revealed variation in their community reconstruction patterns. In some villages, local residents have worked together to demine public spaces and rebuild destroyed infrastructure. However, other neighboring villages have not organized around reconstruction activities. This dissertation project delineates the causes of this variation by tracing the relationship between local conflict dynamics and subsequent village peacebuilding efforts. Despite a rich body of literature on civil wars, social scientific studies have seldom focused on post-conflict settings. Extant research on post-conflict settings has focused on top-down peace programming and failed to consider the theoretical link between conflict dynamics and post-conflict outcomes. By focusing on local reconstruction activities across villages in Colombia, and implementing a comparative, theoretically driven study of the relationship between these outcomes and local conflict dynamics, this dissertations argues for a more explicit link between a conflict setting and its post-conflict landscape. Further, this dissertation delineates how conflict dynamics affect reconstruction efforts through the trust, informal institutions and social networks of villages. Finally, I offer a conceptualization of grassroots peacebuilding and a theoretical framework to help scholars, policymakers, and practitioners understand and identify informal or small-scale reconstruction processes led by ordinary people. Numerous international peacebuilding missions have failed to establish sustainable peace precisely because they have ignored local dynamics, both in transitions from war and in post-war environments. Although international policy circles have advocated for greater attention to micro-level causes of conflict and bottom-up reconstruction processes, systematic research has yet to be conducted on this topic and scholars continue to focus on elite-led peace operations. My dissertation fills these gaps, while providing generalizable insights relevant to the international community and countries transitioning from war to peace.