PLATO
A teaching system at the University of Illinois that, almost by accident, invented chat, forums, email and multiplayer games a decade ahead of everyone else.
Donald Bitzer started PLATO (Programmed Logic for Automatic Teaching Operations) in 1960 so students could take courses at terminals hooked up to a central mainframe. PLATO IV arrived in 1972 with an orange plasma display — which Bitzer co-invented — and a touch panel, and course authors wrote lessons in a language called TUTOR. Control Data Corporation took the system to market from the mid-1970s, with big hopes and modest commercial results.
The interesting part happened in the margins. Users built Notes, Talkomatic and a string of multiplayer games that ate more machine time than the courses did. A complete online culture — flame wars, romances, all-night gaming sessions — existed here before most people had heard the word network.