For over a century, history teachers throughout the United States have selected textbooks as the primary instructional material for their classrooms, while textbook authors and publishers have continuously produced a unified nation-state narrative that presents United States history as a series of objective historical facts for student memorization. Some researchers have suggested that teachers abandon the textbook in favor of primary sources. Yet, due in part to institutional, societal, and political pressures, classroom teachers continue to use these traditional texts. This study, a qualitative investigation of the causal and coherences structures in a sample textbook, a teacher's instructional explanation, and students' related summaries, seeks to determine the influence of a textbook passage and teacher's instructional explanation on students' mental representations of history: What causal and coherence structures are present in a sample US History textbook? To what extent do the causal and coherence structures of the textbook passage influence a teacher's mental representation of a historical event? To what extent do the causal and coherence structures of the textbook passage and the instructional explanation influence students' mental representations of a historical event? Using Kintsch's Construction-Integration Model and Halliday's Systemic Functional Linguistics, data from participants in a diverse setting east of Pittsburgh was analyzed, comparing the network chains and transitivity structures of the passage, the instructional explanation, and participants' summaries. Among this study's findings, students include information common to both the textbook passage and the teacher's instructional explanation in their summaries. Furthermore, the causal constructions identified in students' summaries are similar to those found in either the textbook or the instructional explanation, not often both. These findings have implications for teaching with textbooks, disciplinary literacy instruction, and the implementation of critical, historical thinking in K-12 history classrooms. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]