Great video from the Marin museum detailing the early development of mountain bikes.

[winjohn]

If you haven't seen it already I would recommend it as a highly informative 30 minutes. The most amazing thing for me was at the end they show a dual suspension shaft-driven Pierce bike. Any guesses what year?
The museum guy is asked whether this was the first gravel bike and he gave the best answer ever.
'They were all gravel bikes then...no tarmac roads!