01/01/1974
The first online chat system was called Talkomatic, created by Doug Brown and David R. Woolley in 1974 on the PLATO System at the University of Illinois. It offered several channels, each of which could accommodate up to five people, with messages appearing on all users' screens character-by-character as they were typed. Talkomatic was very popular among PLATO users into the mid-1980s.
The first dedicated online chat service that was widely available to the public was the CompuServe's CB Simulator in 1980, created by CompuServe executive Alexander Trevor in Columbus, Ohio.