This symposium issue of the Drexel Law Review provides an in-depth examination of business improvement districts (BIDs) in Philadelphia, including case studies of each BID in the city, commentary on those case studies by law school faculty (Richard Briffault, Gerald Frug, Nicole Stelle Garnett, and Richard Schragger), and essays by three practitioners (Paul Levy, Lawrence Houstoun, and Dan Hoffman) who have worked closely in and around the world of BIDs, both in Philadelphia and elsewhere. In this introduction, I discuss the case studies and commentaries to provide a brief historical overview of the role of BIDs in Philadelphia, and I will suggest how one may see the role of BIDs in the city as part of a process of institutional evolution.