When you say wilderness areas of North America, you're pretty much talking about some scattered and ever-shrinking parts of the American west, interior and northern Alaska, and interior and northern Canada. There may be some detective or mystery novels set in those regions, but I'm not up on them. On the other hand, I can recommend some good reading that has part of what you're looking for.
If you're interested in the desert southwest, the novels of Tony Hillerman are good detective/mystery stories set in the Navajo lands of Arizona. Not wilderness, of course, but not exactly urban either.
Some of the most truly evocative writing about the wilderness pockets that remain in Arizona are the works of Craig Childs. These are nonfiction essays, but at their best they have the compelling narrative of good mystery fiction, as well as a haunting inner quality. Childs is a talented writer. Look for The Secret Knowledge of Water.
Changing the scene, my old friend John Smolens writes good mystery novels that tend to center on ordinary working stiffs. One called Cold is set in the Upper Peninsula of Michigan--again, not truly wilderness, but it ain't exactly civilized either. John is a transplanted New Englander who teaches writing at Northern Michigan University in Marquette, and he's captured the spirit of the place very well.
Hope this gives you some ideas.
Mike
