From Tracing the Evolution of Social Software, October 13 2004, by Christopher Allen, in Life With Alacrity, a blog on social software, collaboration, trust, security, privacy, and internet tools:

Also, the development of the Michigan Terminal System (MTS) at the University of Michigan in the 1960s had important implication on the development of early online communities in the u.s. mid west. The online conferencing system Confer went into production in 1975.