We conducted a longitudinal field study of nine nascent ventures attempting to revitalize local municipalities to understand how and why identity processes shape organizing in multi-founder nascent ventures. We develop grounded theory and a process model showing how the patterning of founders' social identities shapes early structuring processes, how this in turn influences the construction of a collective identity prototype and its attempted enforcement by an in-group, and how the overall process influences whether or not founders remain engaged in their joint organizing efforts. Our contributions extend the growing entrepreneurship literature on founder identity from an individual focus toward understanding how founding teams work through organizing issues and from a focus on established organizations to exploring why and whether teams move forward in nascent ventures. We open up a series of important questions for future research about how founders become "who we are."