The Adirondacks is the largest park of any kind in the lower 48 states, larger than Yellowstone, Yosemite, the Grand Canyon, and Olympic National Parks combined. It is larger than the state of New Hampshire, larger than six other states. Its six million acres contains more than 2,800 ponds and lakes and 1,500 miles of rivers. Indeed, 90 percent of all plants and animals that exist north of the Mason-Dixon line and east of the Mississippi River can be found somewhere in the Adirondacks.

Yet the Adirondacks and even the Catskills in the southern part of the state remain off the radars of most family travelers, more a coveted secret cherished by northeasterners. Like most tourism in New York, it's overshadowed by the large metropolis that sits in the south. More importantly, unlike Yellowstone, Yosemite, or even Acadia on the Maine coast, the Adirondacks is a state park. It's not even entirely government owned. Within the "Blue Line" delineating the state park's boundary is a mix of public and private lands. Thus, despite its immensity, the Adirondacks will never have the popularity or crowds that swell the national parks in summer—and that is exactly why you should head there.

Days One and Two: Albany to Keene (120 Miles)
Looking out from a lean-to across Heart Lake, in the shadows of New York's High Peaks region, one easily senses the enormity of wilderness that defines the Adirondacks. It's no surprise that the Adirondack Mountain Club (518.523.3441; www.adk.org) built their rustic retreat, the Adirondak Loj, on the shores of Heart Lake. But you don't have to stay in the Loj to enjoy all of the AMC's amenities—37 campsites and 16 lean-tos are nestled on or just off the shores of the lake (lean-tos numbered five through eight offer prime beachfront locales). Families can swim in the water, rent canoes, or go on guided hikes with naturalists from the nearby nature museum.

The mile-long trail to the short summit of 2,876-foot Mount Jo (suitable for any child five and older) climbs through a deep forest of uprooted birches before clambering over the final rocks to reach the top. For such a short climb, the rewards are great. Look above and you'll find Marcy (5,334 feet) and Algonquin (5,114 feet), the two tallest mountains in New York State, standing shoulder to shoulder.

After this little warm-up on, hit the red-marked Indian Pass Trail. This 8.3-mile one-way trek goes through a variety of terrain—rolling cedar and birch second-growth forest, fields of wildflowers and ferns, and waterfalls tumbling into creeks—before snaking through a narrow chute, where cliffs rise some 1,000 feet on either side. It only has a vertical rise of 674 feet, but walking on this rugged rock as it bisects the High Peaks is a good challenge for children eight and up. If you have teenagers who want to bag one of the big boys, take the eight-mile round trip trail to the top of Algonquin (give yourself around six hours). Algonquin's summit offers the finest views from within the High Peaks, without Marcy's standing-room only crowds.