Despite decades of critiques and scores of innovations designed to abolish or weaken it, the school district remains a central institution of the American educational system. Yet, although the district remains the primary agent of local democratic control and serves as the main unit for educational decisions, relatively little attention has been given to the historical evolution of the school district as an institutional form. Reformers and researchers alike often hold misperceptions and inaccurate assumptions about the nature of the school district's development, precisely because the district has been understudied. The authors of this chapter offer a first step toward correcting that oversight by broadening our attention span, providing a solid historical overview of how the district has developed over the past two centuries, and exploring how scholars have analyzed districts at different points in our past. They focus on how the definition of what constitutes a school district has changed over time and on how perceptions of what it has meant to be a good or effective district has shifted throughout our history. They argue that the district has never been a static institution, that its changing forms and functions deserve greater recognition, and that conflicts regarding school districts often reflect deep and enduring frictions that are endemic to American social structures.