Thanks David and Christine. Quite a few municipalities around Minneapolis and Saint Paul had the forethought (or just plain luck) to create large nature parks. They've been upgraded with paved trails, interpretive signs and the like.
These can butt up against commercial projects or freeways, so about a third of time I need to be creative with framing.
I'll scour Google Maps in my area for hints of undeveloped areas with trails, and try to confirm as much as I can with nearby street views.