At 16.5 million acres, Tongass National Forest is larger than some states and more varied. The Alaskan wilderness is filled with huge Sitka spruce, western hemlock and cedar trees – some up to 800 years old! But that's not all, there's also majestic glaciers and icefields. Over one-third of Tongass is designated as federal wilderness, protecting natural habitats for brown and black bears, mountain goats, black-tailed deer, wolverines, river otters, harbor seals and bald eagles among others.

Part of the Greater Yellowstone Ecosystem, Bridger-Teton National Forest boasts 1.2 million acres of land dotted with glaciers, meadows, limestone peaks and hundreds of miles of protected rivers and streams. The forest’s big geological attraction is the Gros Ventre Slide Geologic Area, a long, rubble-strewn scar left behind by an infamous 1925 landslide that blocked the Gros Ventre River and created the five-mile-long Lower Slide Lake.

One of the most popular tracts of public land in the US, Superior can get packed with adventurous travelers who want to kayak, hike, fish, ski and paddle the famous canoe trails of the Boundary Waters Canoe Area Wilderness. Carved by ancient glaciers, this one-million-acre paradise is filled with rugged cliffs, gentle hills, canyon walls, rocky shores and sandy beaches, and dotted with lakes of every size. Superior is also home to the US's last remaining population of gray wolves.

When you think of the southwest, sky islands probably don't come to mind – but that's exactly what make up the 1.6 million acres of Cibola National Forest in New Mexico. The isolated mountain ranges (surrounded by grasslands) can reach elevations of 11,300 feet. Don't miss the Sandia Peak Tramway, the nation’s longest, which carries visitors for 2.7 miles to the top for panoramic views of Albuquerque and the Rio Grande Valley.

Sierra National Forest tends to get overshadowed by its world-famous residents including Yosemite National Park, Sequoia National Park and Mount Whitney, but there's plenty of room for everyone in this 12-million-acre stretch of wilderness. Covering hundreds of miles through California and Nevada, the Sierra Nevada offers towering mountains, granite formations, sub-alpine meadows and crystal-clear lakes as well as sections of both the John Muir Trail and the Pacific Crest trail.

If you love fall foliage, then Pisgah and Nantahala forests in North Carolina are what your autumnal dreams are made of. Every year, the two forests (which total about one million acres including 200 miles of the Appalachian Trail) turn deep shades of red, yellow and orange, coating the Blue Ridge Mountains in a warm glow. But if you can't make it in the fall, Pisgah and Nantahala's swaths of oak, hemlock, tulip poplar pine sycamore, dogwood and beech trees make for a glorious sight year-round.

Spanning more than 800,000 acres, White Mountain National Forest encompasses some of the most natural and beautiful wilderness in the Northeast, drawing visitors with its first-class hiking, skiing and camping. At its center is the 6,288-foot-high Mount Washington, part of the Presidential Mountain Range, which has long boasted the "world’s worst weather." Needless to say, a trek up the mountain is not for casual hikers.

Stretching for 170 miles across southern Utah, Dixie Forest often gets overlooked for nearby destinations like Zion National Park and the Vermilion Cliffs. But not anymore. Dixie boasts giant ponderosa pines and spectacularly colored cliff canyons, including the famous Red Canyon with its brilliant red spires. Other notable spots to add to your itinerary: Navajo Lake and the scenic Boulder/Grover Road on Boulder Mountain.

Head to Green Mountain at any time of the year and you'll find something to do: hiking through colorful foliage in fall, camping and canoeing in summer, picnicing among wildflowers in spring. But winter is the best time to visit this Vermont wilderness, when the forest transforms into a snow-lover’s playground. In addition to three alpine ski areas and seven Nordic ski areas, Green Mountain offers trails, snowmobiles, snow shoes and pretty much any other snow-based recreation.

Two national forests that became one in the 1950s, Washington and Jefferson forests stretch across Virginia, into West Virginia and along the Appalachian Mountains. They're a outdoor enthusiast's paradise with ideal conditions for hiking, fishing, biking, skiing, horseback riding and hawk watching. GWJNF is also home to 2,300 miles of streams, 40 species of trees, 60 species of animals and 50 endangered plant species.