The Canadian tundra version of this is my next door neighbour ploughed the roads in town and would dump the snow in our side yard so we had a big hill to sled down, and we’d build a quinzhee out of the top part of it with our dad every year.
i DESPERATELY wanted a treehouse as a kid, but my parents totally refused, so the best we had was the Community Roadside Bush Hole, where a copse of trees and bushes across the road from the elementary school was crawled into by various kids frequently enough to tamp down a child-sized hidey hole
I'm from Arizona (no tall trees either) and we used to do this with dirt piles whenever somebody in the neighborhood rented equipment, dug out "bunkers" and everything
There was a tree-platform on my grandma's farm but it had an old rug on it that was inhabited by every earwig, so we really never used it. I imagine it was built in the early eighties by some of the first wave grandkids, maybe?
Depending how you define tree house we had several. Lived in the middle of the woods near a neighbor's junkyard so we built jankity ass lost boys villages with orc engineering counterweight elevators and shit. Probably a lot of extremely nearby alternate universes where we all died.
A friend of mine had a treehouse built on a wood frame with plywood sides. Even had shingles on the roof! My favorite part, though, was an old wall phone installed into it with a Batman sticker on it like it was a hotline.
I had a treehouse growing up in Washington state 1978-1986. My dad built it for my brothers and I. It was scary high up in between three trees. Must have been 15+ feet off the ground. Getting in and out was terrifying because the entrance was at an odd angle. No one fell, thankfully. 8)
I remember my dad, with the best intentions, said if I wanted one I had to plan and build it myself
Which at 11 was a challenge of me falling 10 feet multiple times