Western Wyoming is far from flat, and I am sure there are a good deal of trails from Pinedale north, including the Bighorns to the northeast (there is some interesting wheeling in the fairly deep aroyos in eastern wyoming/western nebraska too)... Wyoming had less of a gold rush than colorado, so there are fewer old mining access roads, and there also has been less timber industry, although there are some of both... while I have some family up there, I'm sure someone from the wheeling community will chime in with some more specific references.