In 2010, Illinois policymakers sought to advance statewide school improvement by strengthening school leadership. Illinois became one of the first states to legislatively require a complete redesign of all its principal preparation programs with the goal of ensuring future principals would be "highly effective in leadership roles" and prepared "to improve teaching and learning and increase academic achievement and the development of all students" (Programs for the Preparation of Principals in Illinois, 2016). The new requirements, which went into effect in 2014, called for the reauthorization of all programs and several radical shifts from the status quo. First, all programs had to establish formal partnerships with school districts so that they would be more aware of and responsive to district needs. Second, principal internships required candidates to illustrate the mastery of critical competencies rather than complete observations and log hours. Third, principal training was required to emphasize creating instructional leaders able to catalyze school change rather than developing managers. Fourth, programs also needed to prepare all principals to work with all students from pre-K to twelfth grade, including students with disabilities and English language learners (ELLs). Finally, programs were expected to collect and utilize data for continuous improvement. The current study provides the first statewide, in-depth examination of how Illinois programs and their district partners have interpreted this policy and redesigned their training. Overall, the authors find that Illinois' principal preparation has undergone extensive change. While programs vary, many have made significant alterations to courses, staffing, and district partnerships, and the internship experience has undergone a fundamental change. In this report, the authors will describe these shifts and provide stakeholders' perspectives on their successes and the challenges. The following are appended: (1) Project Advisory Board; (2) Methodology; and (3) Supplementary Data Tables.