Meaningful and sustainable change to undergraduate mathematics instructional practice is needed to support student engagement and success in STEM fields, and this is both a moral and economic imperative in America (CBMS, 2016; PCAST, 2012; TPSEMath, 2015). Historically, change initiatives have not had much success in shifting instructional practice nor in implementing programs known to support students (Burnes, 2011; Henderson, Beach, & Finkelstein, 2011; Seymour, 2001). A limitation of these approaches has been their narrow focus,\ which does not consider the effects of the wider systems (Henderson & Dancy, 2007; Kezar, 2014b). A systems approach to supporting students should consider multiple aspects of students’ experiences with their courses (e.g., tutoring centers, placement exams, classroom experience); a systems approach to change at the undergraduate level should consider multiple aspects of departmental and institutional culture which affect faculty and instructors. This dissertation takes a system-level view of a mathematics department at a large state university (LSU) as they implement a change initiative aimed at supporting student success in Precalculus to Calculus 2 (P2C2) courses by creating a new system, which consists of several interlocking and evidence- based practices for supporting student success. This study does not address the efficacy of those practices nor the fidelity with which they were implemented. Instead, I investigate the culture of the department, how that culture has changed, and how that culture impacted the process of change over a two-year period. This investigation was carried out using social network analysis, climate survey analysis, and qualitative analysis of interviews with members of the department during the period of change. In this dissertation, I discuss shifts in social structure and leadership surrounding the P2C2 sequence and factors contributing to the emergence of new leadership as well as the complex departmental culture and how structures, symbols, people, and power shifted and affected the implementation of new program features (Apkarian & Rasmussen, 2017; Reinholz & Apkarian, 2018). The dissertation concludes with a discussion of the overall experience of the LSU change initiative, practical lessons from their experience, and implications for future change agents or researchers of departmental change.