My first "mountain" bike was a Gary Fisher bike I bought in 1985. It worked well enough for the fire roads in Marin county and surrounding areas but was more of a heavy duty cyclocross bike other than the tires. Cyclocross bikes were not being sold into the USA then nor are they now although "gravel bikes" are similar in many respects.
What has been interesting to me is how in the 1970's it was a contest between the French and Italian bike and component manufacturers and then the Japanese entered the picture and now dominate the bike components market and the largest bike manufacturer in the world is the Taiwanese company Giant.