Activism by U.S. millennials, such as the March for Our Lives, Occupy, and Black Lives Matter, has reversed a national decline in civic engagement. Much of the scholarship has focused on how, not why, millennials participate in activism. This qualitative study of 121 purposely sampled millennial participants seeks to identify the origins of millennial activism. This study operates from a generational lens. Interviews of each participant from 2015-2017 went through two cycles of coding to reveal five progenitors of millennial activism: Family and Friends, Institutions and Organizations, Encounters with Activism, Media and Popular Culture, and Hate and Harm. The study recommends that educators synthesize the progenitors of millennial activism into effective civic engagement pedagogy.