Efforts to cross boundaries separating history classrooms and design studios are hampered by the very different objectives of historical and design teaching. Whereas design requires synthesis and clarity, the study of history should challenge and complicate students’ assumptions about the relationships between design and culture. More importantly, studio-based considerations of historical objects—often through the study of ‘precedent’—necessarily emphasize the formal and instrumental value of a work, while historical knowledge requires instead an emphasis on the ideological and cultural underpinnings of form. This paper views the productive tensions between these differing objectives through the lens of the diagram. The potential for diagramming exercises as components of history-based learning is examined through projects completed by my students in the context of semester-long historical research assignments. These activities complement written work with less traditional procedures that apply diagramming processes to diverse non-formal problems including the evaluation of textual evidence and the mapping of ideological content.