In two experiments, understanding of historical subject matter was enhanced when students acted as historians and constructed their own models of an historical event. Providing students with information in a web site with multiple sources instead of a textbook chapter, and instructing them to write arguments instead of narratives, summaries, or explanations, produced the most integrated and causal essays with the most transformation from the original sources. Better performance on inference and analogy tasks provided converging evidence that students who wrote arguments from the web sources gained a better understanding than other students. A second experiment replicated the advantage of argument writing even when information was presented as an argument.