This article describes the process for creating an evidence-based professional learning (PL) competency framework for people working in the informal science learning field. The project reviewed PL literature, models, and frameworks. Applying what we found to a field which lacks any unified career pathways, we determined a career stage approach would be appropriate. Content--competencies, tasks, skills, and attribute--was obtained through a DACUM workshop held in three cities; each panel represented either early, mid, or mature career stages of employees from across job categories. Thirty-four panelists from 18 museums participated with 1,006 professionals in informal science education institutions participating in the verification study. Looking across these findings and the reviews done previously, we identified trajectories of competencies that changed over time. We named four domains of work and labeled the competencies across career stages for duties within each of the domains. Field testing and research revealed the framework to be valuable and applicable. This work has led to questions related to career pathways, career progression, and professionalization of the field.