The purpose of this study was to explore the effectiveness of training in decision-making on U.S. history content knowledge and on decision-making competence. All sophomores (n = 387) in one Pacific Northwest high school were randomly assigned for two trimesters to one of two groups: (a) U.S. history instruction integrated with decision training or (b) traditional U.S. history instruction. During the study, Experimental Group participants were trained to use a decision-making tool to sort, process, and analyze the facts, events, and concepts of history in the context of solving a historically relevant problem. By applying the decision-making tool to problems and decisions of the past, students utilized a schema for critical, analytical, and creative thinking about U.S. history content. Students also analyzed current problems and decisions they face. Dependent measures were (a) NAEP U.S. History questions, (b) Decision-Making Competence Index (DMC), (c) NAEP item analysis using knowledge forms and intellectual operations, and (d) Experimental Group follow-up interviews. Results indicated statistically significant differences between groups favoring the Experimental on both the NAEP U.S. History test and on the DMC. Experimental Group participants scored higher on NAEP items requiring concept or principle knowledge forms and on items requiring summarization or illustration. Follow-up interview scores positively correlated with DMC posttest scores. Results are discussed in terms of (a) the application of NAEP and DMC scores to curricular interventions and (b) item analysis and interviews in relation to the environmental and physical constraints of the current high school structure.