There is 'Trek Bicycle' video on YouTube called "The History of Mountain Bike Wheel Size".

The video is by Gary Fisher, the man who funded the creation of the moulds for 700c WTB 29er Nanoraptor and the earliest bikes made to fit them.

Without Gary Fishers backing the 29er movement would probably have never have happened. He had learned that large wheel tyres were a good idea after importing Finish show tyres from English pioneer Geoff Apps in the early 1980s. Based on this experience he spent his own money to manufacture a fat 700c tyre that would not fit existing bike frames. He then went on to develop 29er frames and encourage others to make 29er suspension forks.