Research has shown that African American girls are interested in science but not as likely to pursue science-related careers as their white or male peers. Although out of school time (OST) science, technology, engineering, and math (STEM) programs have been presented as means to address this discrepancy and support scientific identity development in girls and students of color, programs specifically for African American girls have not been studied in detail. Additionally, the challenges associated with creating and sustaining OST STEM programs have not been examined. This study explores the evolution of one OST STEM program for African American, middle school girls over the course of three semesters. Using a combined framework of activity theory, communities of practice, and critical race theory, the contradictions within each stage of the program were identified and viewed as opportunities for expansion of the activity system. Results indicated that a consideration of dominant ideologies, or tertiary tools in the activity system, as well as the cultural and historical context of the activity system were necessary to understand and resolve tensions in the system. Implications of this work for researchers and others interested in OST STEM Programs include the need to focus on the interaction of components within activity systems and to identify contradictions within systems in order to support the establishment of a community of practice in the OST STEM Program.