This article empirically investigates the process by which a digital infrastructure evolved and took the architectural form of a digital platform as a core–periphery structure over a 20-year period. Our study pays special attention to the developmental dependencies of the components of the infrastructure’s installed base and how the interdependencies between the platform core and periphery evolve over time. We use the notion of ‘generative entrenchment’ to provide an account of the formation and unfolding of a core–periphery structure from an evolving digital infrastructure that highlights three aspects of the process. First, the process of architectural evolution that our study depicts comprises three phases showing a gradual reversal of the entrenchment relationship of the platform core and periphery: (1) entrenchment of the periphery, (2) mutual entrenchment of the core and periphery, and (3) entrenchment of the core. Second, we show how the generatively entrenched infrastructure’s installed base shaped the decisions and choices regarding the initial platform core. Third, we identify three architectural practices (creating redundancy in the core, augmenting the core with novelty, and reducing the heterogeneity of an entrenched peripheral component and later integrating it into the core) that weakened the entrenchment of the peripheral components, amplified the role of the core, and consolidated the core–periphery structure.