Tennis for 2 - William Higinbotham 1958
SAGE system - USAF late 1950s
Mother of All Demos - Douglas Engelbart SRI 1968
Ivan Sutherland in The Ultimate Display 1965:
The ultimate display would, of course, be a room within which the computer can control the existence of matter. A chair displayed in such a room would be good enough to sit in. Handcuffs displayed in such a room would be confining, and a bullet displayed in such a room would be fatal. With appropriate programming such a display could literally be the Wonderland into which Alice walked.