I'm aware of many version control systems: CVS, SVN, TFS etc...
I've googled for the very first "revision control/version control system" and seen various conflicting answers.
When was source control invented? Who invented it? What was it called?
Here is a pretty decent timeline of the major players in video form (no sound).
It suggests that SCCS was first, by a margin of about 9 years.
There is a lot missing off there though, as evidenced by this blog and the resulting comments.