However, there are about half a dozen "big" complexes of wilderness in the lower 48--places where wilderness areas--either within or without national parks--are stacked on top of each other, creating an environment where relatively vast areas are designated and federally protected as true wilderness, pierced by very little on the way of human development. In making this claim, I'm adopting a somewhat less strict application of wilderness--for example, I'd note that Yosemite National Park is 95% wilderness area, encompassing the Yosemite Wilderness. The fact that you can drive into Yosemite valley itself and hang out with the circus of tourists is--occasionally--unfortunate, but it doesn't really significantly detract from the fact that Yosemite National Park is by and large a wilderness experience. Bounded as it is by further designated wilderness areas, I'd say that the High Sierras Wilderness Complex (my own terminology, not one that's official) which has back to back federally protected Wilderness areas with very little interruption all the way from the Kiavah Wilderness, down near Weldon, CA all the way nearly to Lake Tahoe is truly one of the great wilderness areas on the lower 48, although it's heavily used by hikers and tourists, and most of the big carnivores of a bygone era (i.e. wolves and grizzlies) have long been extinct from the area. Another similar area exists up in Washington--the North Cascades National Park Complex (which includes the Ross Lake and Lake Chelan National Recreation Areas) are separated from other protected wildernesses in the Snoqualmie National Forest and elsewhere in the North Cascades Range by the occasional highway that leads to the Seattle area from the interior, but a handful of road crossings don't significantly diminish the fact that there's a very large area of beautiful mountain terrain that is protected as wilderness. The Pacific Northwest being one of the main hubs of the concept of wilderness chic and the hiking as a lifestyle movement, some of this area is also over-used by tourists (the Enchantments area in Alpine Lakes Wilderness, for instance, has a fierce lottery action ongoing during the summer season for camping permits). This area also lacks large predators (except the black bear)
I think the Colorado areas struggle to really quality, since they are more developed, and true wilderness areas are often smaller, and split apart by roads, towns, and other developed features that make the wilderness areas more like a patchwork than a true complex. But in the more northerly Rockies, we have the massive Greater Yellowstone Ecosystem region, pierced by a handful of roads into Yellowstone and Grant Teton National parks, but otherwise including some of the most remote wilderness in the entire lower 48, the gigantic Bob Marshall and Glacier complex, and the vast and extremely remote Salmon River Mountains complex in central Idaho.
Big wilderness designations also cover parts of southern Utah's Colorado Plateau and the Death Valley region. And, of course, smaller pockets of wilderness dot much of the lower 48's western states. Northern California has some spectacular areas in the shadow of Mount Shasta like the Russian Wilderness and the Trinity Alps Wilderness. Oregon and Washington and Colorado all have tons of spectacular wilderness, including one of my favorites that I've actually been to, the Weminuche Wilderness in southern Colorado, which--although maybe it doesn't qualify as a mega-complex like the High Sierras or the Yellowstone region, but it's still pretty big.
The Wyoming and Montana wildernesses, as well as somewhat the Idaho Wildernesses, are famous for the success of the grizzly and gray wolf in the area, as well as all kinds of other big, charismatic wildlife--bighorn sheep, mountain goat, bison, pronghorn, elk, moose, coyote, and more. These really make these bastions of an America that was, but remains only in small islands in the lower 48 (and still remains somewhat true in vast stretches of the northern Canadian and Alaskan areas, however.) Remote, hard to reach, often lacking in tourists (except for small pinprick areas that get loads) ranging with large and potentially dangerous wildlife; these vast wilderness complexes are something that I, at least, value greatly and desperately wish to further explore. If I could do it all over again, would I have gone into some career where I could range through these wildernesses myself? I don't really see myself as a ranger, but maybe some kind of academic who studied wildlife therein?
I dunno. Maybe. As it is, my goal is to start exploring some of these areas that I've only lightly touched on. I've spent a very brief amount of time in the Sierras, and I spent an equally brief amount of time in Glacier NP. This coming summer, a whirlwind tour of the Yellowstone and Grand Teton national parks will whet my appetite for more. But it's really probably the next summer after that that I'll start doing what I really want to do--weeklong hikes into the backcountry of some of the greatest, most beautiful , and most remote areas of the lower 48 United States. Maybe even, someday, I'll hike the Pacific Crest Trail and the Continental Divide Trails--and soak myself in the wilderness for months.
Here's just a few images that I grabbed from summitpost.org; one of my favorite sites about hiking and mountains, of some of the wilderness areas described in this post.