In 1971 Intel created the 4004 the world's first microprocessor. In 1975 the Altair was the first home computer kit. The Apple II appeared in 1977.
All of which makes Doug Engelbart's 1968 demo even more impressive. A GUI, a mouse, controlling a computer over a network, the concept of WYSIWYG, cut and paste, key combinations, manipulating files, and much more.
I'm not sure whether Doug and his associates completely invented the modern computer and the modern computer interface from scratch... or whether his ideas were so good no one has bothered to advance the state of the art much. So much of how we interact with our computers is just a refinement of what Doug demonstrated in 1968. Sure it's faster, slicker, and prettier today but that's to be expected.
Without further ado... may I present... The Demo.