The terrorist attacks of September 11, 2001, spawned 252 new nonprofit organizations. We know little about these organizations, including how they emerged, formalized, met constituents' expectations for immediate performance, and ultimately survived. This article explores these issues through a case study of one successful organization, the Windows of Hope Family Relief Fund. Using concepts from disaster, organizational ecology, and entrepreneurship research, the analysis identifies six propositions that link these literatures, notably the role of resource acquisition in formalization and the role of legitimacy in both fund development and organizational endurance. The study contributes new knowledge about the role of collaboration in acquiring capacity to enhance responsiveness. The findings suggest potential parallels to the evolution of new nonprofit organizations in other contexts.