Why are American INGO foundings declining while there is still a great deal of unmet social need and available resources? This chapter argues that INGO foundings respond to population density. We test our argument in two ways. First, we use data drawn from tax records on American INGOs to establish that there is a curvilinear relationship between population density and foundings. Second, we present a qualitative case study of civil society and democracy INGOs, drawing on memoirs, document analysis, and interviews with INGO founders and long-time practitioners. The case study uses process tracing to demonstrate how the extent of mutual support vs. competition shifts in a population as density increases. Finally, the chapter concludes by extending our argument about INGO foundings to INGO deaths.