Suicidology and suicide prevention are relatively new fields of study in the United States, but they have made significant progress since their beginnings. This study aimed to identify the most impactful theories in the history of science and suicidology and the most impactful events in the suicide prevention movement. These theories and events were identified through expert nomination. The most impactful theories were those of Shneidman, Durkheim, and Joiner. The most impactful events included the opening of the first suicide prevention center and hotline, the founding of the American Association of Suicidology, and national publications (e.g., "National Strategy for Suicide Prevention"). (Contains 2 tables.)