This book presents the catalog of a virtual exhibition featuring different visualizations of the structural evolution of 51 Web APIs of different sizes and shapes, showing how they mostly grow but sometimes also shed some dead branches over the years. The diagrams are drawn based on the exact OpenAPI specifications as they were versioned on some open source repository. While there are many books on how to improve the design of existing APIs, the goal of this book is to show a small sample of actual API designs undergoing change. Learn from these examples to avoid false starts and discover which structures turn out to be stable over the years. All APIs represented are Web APIs: they come from the age when many attempted with very different results to use the HTTP protocol to remotely invoke software delivered as a service. The APIs have been selected mainly due to their visual appearance.