We describe the propagation of a technology-based educational innovation through its first 3 years of public use. The innovation studied is the Concept Warehouse (CW), a database-driven website developed to support the use of concept-based pedagogies. This tool was initially developed for instructors in undergraduate chemical engineering courses, but has spread to other disciplines as well. In this time, it has grown to over 650 registered instructors representing over 170 institutions. While this study is specific to a particular case, the intent of this article is to provide an exemplar of real-time propagation that informs other researchers and developers. We frame our analysis with Diffusion of Innovation Theory and use a design research methodology that focuses on communication channels, types of knowledge, and stages of the innovation-decision process. Data sources include usage records and survey responses which are analyzed with network diagrams and non-parametric statistics. We find that in comparison to mass media, interpersonal communications tended to result in higher proportions of how-to knowledge and implementation. Three types of opinion leaders were identified through user data and network diagrams. All played critical roles in the tool's propagation, especially the project collaborators--opinion leaders who actively promoted the CW, in part, because it also propagates their own innovations. Finally, users with self-identified prior principles knowledge showed statistically significantly greater progress in gaining how-to knowledge, but no significant difference in progressing to the implementation stage of the innovation-decision process when compared to users without.