Over the last several years, government has invested heavily to create state longitudinal data systems. Policymakers stand poised to make use of these new systems to inform decision making in ways that were not possible in the past. Building such data systems requires the formation of complex networks involving the coordination and cooperation of large numbers of actors. Building these networks is no easy task and must be undertaken with careful planning. Employing Thomson and Perry's collaboration framework as a tool for analysis, this article examines the construction of one such data system, the Illinois Longitudinal Data System (ILDS), and offers lessons learned based on the successes and failures of its development. Findings focused on the role that negative histories and mandated formation play in network development.