In this high school U.S. government and U.S. history curriculum unit, students examine in depth the expansion of the North Atlantic Treaty Organization (NATO). Detailed activities are provided to teach students about the origins of NATO, its impact on U.S. foreign policy, and its future directions, particularly the enlargement of NATO in the post-Cold War world. The materials include informational handouts for students, background information for teachers, lesson ideas and outlines, black line masters, rubrics, application to civics and history standards, and primary source documents, including the correspondence of key figures in the history and development of NATO, newspaper articles, and transcripts of Congressional testimony. (RJC)