The proposal for a playful Los Angeles is an invitation for community involvement in developing how playful spaces might be valued and implemented within the city’s urban fabric. We find that the Expo Line is a particularly appropriate system to experiment with because it reaches a diverse group of users and is a large part of daily life, particularly in communities with high populations of youth. We believe that through community engagement, prototyping, and the piloting of open-ended playful spaces, a sustainable city can be discovered while being built upon existing urban systems. The goal of the book is to become a cornerstone of outreach towards recognizing a playful Los Angeles, where equitable opportunities for play are made easily available for people to discover in their daily lives.