The remarkable degree of religious diversity in the United States is produced more through schisms and mergers occurring to preexisting denominations than through foundings of new religious groups. In this article we analyze schisms, focusing on mainstream Protestant denominations over the period 1890–1990. We treat schism as an organizational process rather than an expression of purely doctrinal disputes; more specifically, we argue that schisms arise from within denominations in response to attempts by denominational elites to achieve organizational consolidation. Event-history techniques are used to test hypotheses concerning resource environments, effects of denominational reorganization, resource mobilization capacity, network linkages, and denominational centralization. Results show that rates of schism are influenced by prior structural changes, size, and linkage to a liberal federation; we find no effects of resource or institutional environments.