This dissertation explores the un-written story of American foreign assistance, agendas and practices in Romania during the First World War and in the interwar period. In five core chapters, this dissertation highlights humanitarian responses and extension of philanthropy to relieve, rehabilitate, and modernize Romania’s population and the country’s institutions. These chapters focus on emergency relief in times of war, the relief and rehabilitation of children, humanitarian efforts on behalf of Jews, as well as modernization of health structures and knowledge production institutions. This dissertation shows that Romanian state and non-state elites interpreted and received American assistance primarily as an accelerator of domestic practices of nation-building. Furthermore, American aid represented an alternate avenue to strengthen individual, social, and political agendas during the transformative period of the new Greater Romania nation-state. Thus, this dissertation highlights that Romanian channels of reception interpreted American aid as a tool to strengthen autonomy and address social volatility and underdevelopment after the First World War and in the post-Unification period.