AbstractSociologists of U.S. higher education have emphasized the sector’s historical expansion, which has limited the attention given to the dynamics of organizational closure. Drawing on an original dataset comprising colleges and universities across all sectors and tiers, we show how general expansion is tempered by 354 organizational closures between 1944 and 2018. Closures cluster in time between 1964 and 1974 and after 2008 reflecting shifting causes of and responses to legitimacy loss. Analyses provide support for hypotheses drawn from institutional theory, and, while controlling for a number of variables, identify two main causes of college mortality. These are demographic exclusivity, i.e., women’s and (historically) Black college status, and accreditation. Mortality of exclusionary institutions is further associated with social activism and the system-wide diffusion of related group-differentiated study programs, particularly in the period 1944–1979. By contrast, accreditation becomes more important in the post-1980 period.