Enthusiasm about the instructional potential of primary sources dates to the late 19th century and has been echoed recently in the work of literacy experts, historians, and educational psychologists. Yet, no extended intervention study has been undertaken to test the effectiveness of primary source instruction in real history classrooms. This study, with 236 eleventh-grade students in five San Francisco high schools, represented the first large-scale extended curriculum intervention in disciplinary reading in an urban district. The Reading Like a Historian (RLH) curriculum constituted a radical departure from traditional textbook-driven instruction by using a new activity structure, the "Document-Based Lesson, " in which students used background knowledge and disciplinary reading strategies to interrogate, and then reconcile, historical accounts from multiple texts. A quasi-experiment control design measured the effects of a six-month intervention on four dimensions: 1) students' historical thinking; 2) their ability to transfer historical thinking strategies to contemporary issues; 3) their mastery of factual knowledge; and 4) their growth in general reading comprehension. MANCOVA analysis yielded significant main effects for the treatment condition on all four outcome-measures. Qualitative analyses of videotaped classroom lessons were conducted to determine the frequency and nature of whole-class text-based discussion. Only nine whole-class text-based discussions were identified in over 100 videotaped classroom lessons, despite the presence of instructional materials explicitly designed to support student discussion of debatable historical questions. Analysis of teacher and student participation suggests a relationship between active teacher facilitation that reviews background knowledge and poses direct questions about texts and higher levels of student argumentation. This dissertation is structured as three free-standing papers, each of which addresses one aspect of the larger study. In the first paper, I discuss the design of the quasi-experimental study and report quantitative findings. In the second paper, I locate teacher facilitation of whole-class historical discussion in the literature on classroom discourse, and I propose a developmental framework for analyzing student historical argumentation in classroom discussion. In the third and final paper, I discuss the theoretical underpinnings of the intervention curriculum and offer two examples to illustrate the structure of the "Document-Based Lesson.".