On December 9, 1968, Douglas C. Engelbart and the group of 17 researchers working with him in the Augmentation Research Center at Stanford Research Institute in Menlo Park, CA, presented a 90-minute live public demonstration of the online system, NLS, they had been working on since 1962. The public presentation was a session in the of the Fall Joint Computer Conference held at the Convention Center in San Francisco, and it was attended by about 1,000 computer professionals. This was the public debut of the computer mouse. But the mouse was only one of many innovations demonstrated that day, including hypertext, object addressing and dynamic file linking, as well as shared-screen collaboration involving two persons at different sites communicating over a network with audio and video interface.
It's interesting watching the demo. There's a keyboard in the center, a rather large unergonomic looking mouse to the right, and a 5-key chorded keyboard to the left. Other than the shape, the mouse is easily recognizable as a mouse (a three button mouse no less). The chorded keyboard is rather odd (and something that didn't make it in today's mass market). The features include composition, editing, linking (like links used on the web today, but possibly more sophisticated) and collaborative work being done on two computers at the same time.
It would be an impressive system today. Back in 1968 it was mind blowing.
But he wasn't the only one working on hypertext at the time—there was Ted Nelson and his work on Xanadu (which has yet to be finished today).