This chapter examines the teacher learning that occurred in this project as a process situated within an institutional context and how both process and context interact reciprocally to support development. It draws evidence from a large data corpus gathered over a 5-year period and consisting of teachers' reflections and written work, students' written work, observations of classrooms and seminars with teachers and principals and administrators, and interviews with teachers and principals. The chapter describes how the school district in which we worked helped build capacity for teacher change so that algebraic thinking was supported, made intelligible to teachers, integrated as a regular part of instruction, and related to other district priorities and initiatives. It organizes our discussion around some of the areas that we have come to view as essential in helping teachers algebrafy their classrooms. The chapter describes the ways in which the authors observed a district build its capacity to support teachers in algebrafying their classrooms.