@deorman and
@OddJob, the Marin guys know full well that folks were modifying bikes for offroad use long before they started; GF mentions it in a video from that time period, they hung out with/partnered up with John Finley Scott, who'd been doing it in the 50s; they knew that guys had been doing it on Tam long before they started to, and obviously all riding was "offroad" before paved roads became prominent in the USA. The difference between CKelly, GFisher, TRichey, etc is that they went from modding production bikes from other factories to designing/fabbing their very own purpose-built offroad bikes... and later, they had them made overseas, but really, that's the difference.
@OddJob and
@deorman may have been doin' it pre-70s, and they may know of others who did it before them, but nobody else made that leap from changing a few components to make a street bike offroad-worthy to producing actual trailbikes from the ground up, on a grand scale.
I think that's a worthwhile distinction to make, don't you?