I like the concept from the Wilderness Act of 1964:

“A wilderness, in contrast with those areas where man and his own works dominate the landscape, is hereby recognized as an area where the earth and community of life are untrammeled by man, where man himself is a visitor who does not remain.”

(By the way, I used to read "untrammeled" as more or less meaning "untrampled," but it really means "not limited or restricted; unrestrained.")

I also think of "wilderness" in terms of its root "wild" (or "wilder").  It's a comparative concept:  that which is wilder.  There's a whole lot of wilder-ness in the BW/Q, even it it was logged and has maintained portages and campsites.