This article describes how redesigning a program's assessment practices for teaching with primary sources (TPS) can provide a clear framework for talking about the impact of educators' work in archives and can provide feedback on how to refine instruction practices for greater results. The authors share a description of their assessment redesign process accompanied by analysis of the implementation of our new assessment tool in the hope others will consider the design and goals of their own assessment practices. The authors' work demonstrates that reflection on existing tools, development of new goals, and design of new assessment strategies can yield inspiring new data on program impact and highlight areas for improvement. By illustrating the authors' redesign process, this article also demonstrates the types of impacts and outcomes that educators can measure for TPS and points to the huge potential of TPS in local history contexts and elsewhere. The authors' revised student assessment moved archives staff from relying on self-reported, affect-focused data to better understanding the outcomes of their work with students: the impact of project-based learning in archives; the value that students find in various aspects of their encounters with archives; the role that TPS in local history contexts plays in connecting students to their community; and the transferability of research skills that students learn through TPS activities.