Back in 1968, Douglas Engelbart demonstrated a number of new technologies. These included the mouse, hypertext, real-time editing collaboration, and videoconferencing.  This demonstration, which is nearly 50 years old, is amazing for the numerous technologies that were introduced as breakthrough technologies — almost all of which are commonplace parts of our world today. For our 300th video, we present this historical demo, far less exciting in its presentation than what we get from Silicon Valley, but far greater in its impact than almost any presentation before or since.