Disciplinary literacy encompasses not only the ability to read the texts of a discipline, but also to engage in the practices and discourse of that discipline. At the center of the discipline of history is inquiry. For these students to move from their ninth grade expectations about history toward the authentic discipline of history, they would need to become increasingly capable readers who could grapple with a wide range of history texts. The authors hypothesize that reading and shared discussion of historical sources can build students' understanding of history as an interpretive enterprise and their ability to engage in historical argumentation. Students argue to make sense of the history texts they are reading and to work out their historical interpretations. As such, we consider these text-based discussions to be incipient historical argumentation. This discourse may serve as the foundation for written argument at a later stage in the process. It is also part of disciplinary literacy. Project READI recognized the central role teachers play in mediating the learning opportunities of students and, thus, invested in developing design partnerships that fostered two-way learning between teachers and researchers. The students experienced the epistemology of history - the limits of the historical record, history as interpretation, history as inquiry, and the relationship of the history they had learned to the present.