My research focuses on the role of historical legacies in shaping conflict dynamics and reinforcing social divisions today. I highlight the importance of equity in creating effective long-term governance and resilient institutions. Using the Philippines southern region of Mindanao as a case study, the three papers in my dissertation come together to provide evidence that the robust relationship between ethnic homogeneity and institutional development may not hold consistently over elongated time frames. I argue that while homogeneous communities are often quicker to organize through informal norms, the slower process of channeling regulations through structured, fixed institutions may sacrifice short term efficiency in favor of long-term durability. Viewing fractionalization as a process, I argue that this institutional trajectory will only unfold when examined through a historical lens and if fractionalization occurs in ways that incentivize collaboration instead of competition between groups. My first paper highlights the importance of a mutual investment in exchange across groups for setting communities on a path towards resiliency to communal conflicts. I argue that communities with histories of religious and ethnolinguistic diversity, alongside intergroup exchange, are more likely to invest in formal processes to resolve disputes, which in time leads to more robust institutions to mediate conflict between groups. I use 1939 census data on local dialects to show that contemporary Peace Zones are more likely to form in areas where members of the majority group invested in learning minority languages historically. The second paper provides evidence that the process of fractionalization, rather than just fractionalization itself, will carry long term consequences for institutional development. I argue that increased ethnic fractionalization during times of low conflict can break down political dynasties, which strengthens long term government responsiveness. Using census and administrative data, I show that where municipalities had higher levels of fractionalization prior to the mass migration and discriminatory laws initiated by US colonial authorities there are higher ratings of local government efficiency today. However, sharper demographic changes during the period of mass migration are associated with decreases in contemporary local government efficiency. The third paper uses original survey data collected on the management of land conflicts to explore where and why some local courts show more bias against minority groups. Survey results show that local government officials are more likely to expect community courts to rule in favor of minority groups in communities that fractionalized prior to mass migration. However, sharper demographic changes during mass migration are associated with a decreased expectation that a member of a minority group will accept the ruling of a local court. I provide evidence that historical institutional arrangements are generating path dependencies by showing that historical fractionalization prior to mass migration is associated with the development of fixed institutions to resolve conflict across multiple time periods historically and today. These papers provide theory and evidence of enhanced institutional resilience and an ability to adapt to new challenges or opportunities in communities with histories of intergroup cooperation. While fractionalization may initially weaken coordination, the institutional arrangements designed to overcome this new barrier can promote long term durability and strengthen a community's ability to effectively manage future conflicts.