Research indicates that most American citizens know little about Islam and, specifically, the major differences between Sunni Muslims and Shiite Muslims and why this matters to the United States. Although the two major Islamic factions share many common core beliefs and practices, there are some significant religious and political differences dating back to the disagreement over the succession of leadership in the Muslim community after the Prophet Muhammad died in 632. Indeed, sectarianism has played a pivotal role in the turbulent geopolitics of the Middle East for centuries. Islam must be studied for its contributions and role in world history. Therefore, it is crucial that social studies educators teach not only the core beliefs, rituals, and history of Islam but the differences between Sunni and Shiite Muslims. This knowledge is vital if Americans are to make prudent decisions regarding support for specific foreign policy positions and decisions regarding Islam and Muslim countries. This article describes and explains the differences between Sunni and Shiite Muslims and discusses the implications for the United States and social studies education. Finally, the article shows how Islam can be implemented in the NCSS C3 Framework.