This research study examined nine secondary American history textbooks regarding their treatment of 9/11 and related events. The analysis centered on both the knowledge included and excluded from the discussion in each book. Particular attention was given to the moral and ethical issues relevant to 9/11. Findings show that textbooks vary in their descriptions, but most omit important information and disregard important moral and ethical aspects of historical events. These exclusions legitimized and validated particular foreign and domestic policies. More importantly, they limited the perspectives that students could consider, constrained possible alternatives, and avoided ethical concerns and issues. (Contains 4 tables.)