The term “Great Observatory” was once a piece of programmatic branding for four space telescopes launched between 1990 and 2003. No longer. While Hubble, Chandra, Compton, and Spitzer will reign as everlasting triumphs of science, the term “Great Observatory” has transcended these missions alone. It now reflects a vision for transformationally powerful, flexible, and long-lived facilities enabling panchromatic synergy, near-simultaneity, and acting as force multipliers for ground-based facilities around the world. With extended missions that can span decades, Great Observatories become something other than a pursuit of important but narrowly-defined science goals. They become discovery platforms for the questions we have not yet thought to ask. In this talk, I’ll review the past, present, and future of the Great Observatories program, particularly in the wake of Astro2020.