Given the trends of increased teacher activism and civic engagement, and the implications of this shift for teachers and schools in general, we need a better understanding of how teacher activism connects to teachers' views on professionalism. The purpose of this study, then, is to better understand the current growth of politically engaged, activist teachers and the connections they draw between their activism and their role as educators. This study addresses an identified gap in the education reform scholarship around the relationship between teacher activism and teacher professionalism. Education research has looked at teacher activism and a number of different interconnected issues, such as identity (Picower, 2012); unionism (Weiner, 2013); leadership (Little, 2003); and online social networking (Baker-Doyle, 2017), but very few studies have explored teacher activism as it connects to professionalism. Yet without this research, we are left with an insufficient understanding of both what it means to be a teacher in the 21st century U.S. and the ways in which teachers themselves can be agents of social and educational change. Drawing on semi-structured interviews, twelve-months of observations and document analysis this qualitative study explores the experiences of twenty-five teacher activists. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]