It's only fair to mention that the first distributed version control system was created by Reliable Software (www.relisoft.com) back in 1996. It's called Code Co-op and it's now available in version 4.6.
The creator of BitKeeper, Larry McVoy started working on his system about the same time. Code Co-op was first demoed at the Seventh International Workshop on Software Configuration Management, where I gave a talk about server-less version control systems.
If you Google "distributed version control", you'll get Code Co-op as one of the top hits (Monotone beats it, because open-source projects tend to get better ratings on Google).