It was on 19 June 1984 that Bob Scheifler announced the initial X window system release "X1" at MIT. It wasn't until 1987 though that X11 was drafted as marking the protocol's current version albeit evolved a lot since the 80's.
When X was introduced, its performance was "about twice that of W", the prior window system out of Stanford. X also marked the first window system that was vendor and hardware independent.
Those wishing to reminisce over the X window system can see a copy of the original X announcement . Those wishing to relive the X history can also visit Wikipedia if looking for some fun Monday reading.
How long do you suspect until the Linux desktop is effectively Wayland-only, with X11 cruft largely a legacy remnant?
— Phoronix (@phoronix) June 20, 2022