This chapter examines the history of conspiracy theories, primarily in the United States, during the twentieth and twenty-first centuries and their relationship to disinformation and misinformation. In analyzing the development of the Deep State and New World Order conspiracy theories from the Protocols of the Elders of Zion from 1910s to Pizzagate and the first Trump Presidency in the 2010s, the chapter argues that conspiracy theories rest on two main drivers, namely the fear of excessive governmental and elite power, and the fear of political, cultural, and economic change. These fears are reflected in reaction political, societal, and cultural developments and they often have a rational and factual basis, even if the narratives presented have little basis in reality. The chapter further argues that the relationship between disinformation, misinformation, and conspiracy theories is important and intertwined. Disinformation and misinformation are not responsible for creating conspiracy theories but can help sustain and deepen them as they become anchors and evidence in narratives about power and human agency.