First jump was on my JR50, grandma's neighbor had a hump on the side of their driveway, i hit it WFO and launched into the side of their house lol. Never jumped again until i was on a KTM SR.50
I was on a 1977 Yz 100 at a place that was called the sand pits or brush road it was off Euclid Ave by Brush Road (which has now turned into the hood) Went back to check it out a couple of years ago and the tracks were overgrown but the 20 acres of trails were still there. Road it a few times until I rode up on some crack heads doing who knows what back there. Pretty sketchy considering I had my daughter who only 7 or 8 at the time with me.
Dirt pile somewhere in licking county on a rusty huffy. Been too long ago, but I am sure that the first jump that I hit on a bike was actually on my bicycle.