This document outlines the evolution of the learning health system over 5 chapters from the 1970s to the present. It discusses early databases and online networks in the 1980s that hinted at a new approach for sharing patient information. Foundations were established in the 1990s through electronic medical records, registries, and decision support tools. A vision for a national health information infrastructure emerged in the 2000s along with policies to promote it. The current focus is on building out this infrastructure through health information exchange platforms and other technologies, though challenges around privacy, standards, and financing remain.