Tree Following: tree in a tree & a geography challenge

Where was I?

The large trees on the shore of this small shallow lake, one of many such lakes in the area, are Plains cottonwoods. Note they have green leaves in October. And the wind isn't blowing, just a light breeze. Obviously I wasn't home in Laramie, Wyoming.

While trying for artistic shots of gnarled bark, I noticed a small green ash tree growing out of a cavity in the trunk of a cottonwood.

I thought for a while about how this might have happened. Maybe the winged seed (samara) landed and germinated where enough debris had accumulated for the seedling's tiny root to keep it in place. Certainly enough rain (ann. av. 24") and snow (ann. av. 33") falls here to sustain it. But what does the future hold? Will the green ash live on when the cottonwood senesces, dies, falls? Will large recreational vehicles continue to fill the campground nearby? Will there still be a skiff or two on the lake at sunset?

Back to the challenge: Where was I? Specifically, in which US state and which quadrant (SW, SE etc.)? The next photos may be helpful. You can post your answer as a Comment, but sorry ... no prizes.

Clue on the horizon.

View from the top: trees galore, prairie in the distance.

This particular state quadrant was the destination of a recent trip. Blog posts to follow.

This is my contribution to the December gathering of tree followers, kindly hosted by The Squirrelbasket. More posts here. With no news about my tree (it's winter in Laramie), I'm reporting on trees elsewhere.