The X Window System

Before X.org came along, I made a note of this:

The last wide-spread functional enhancement exported by the X server might well be the Shape extension, designed (in the hot tub) at the 1989 Winter Usenix in San Diego. (quoted from here

These days most people use (or are only aware of alternatives like Terminal Services, VNC, or NX, but the ancient lore is still valuable.