This thesis examines the massacres of the Plains Indian Wars in the United States (1851-1890) and how they relate to contemporary theories of genocide. By using the Plains Indian Wars as a case study, a critique can be made of theories which inform predictive models and genocide policy. This thesis analyzes newspaper articles, histories, congressional investigations, presidential speeches, and administrative policies surrounding the four primary massacres perpetrated by the United States during this time. An ideology of racial superiority and fears of insecurity, impurity, and insurgency drove the actions of the white settler-colonialists and their military counterparts. Still, despite the theoretical emphasis on massacre in genocide theory, massacres on the Plains were relatively rare compared to the use of other genocidal tactics. This demonstrates that contemporary genocide theorists must be careful not to unintentionally limit thinking on genocide to strict military or militia led violence.