You’ve spotted geysers in Yellowstone, hiked to waterfalls in Yosemite, and pedaled the Cades Cove Loop in the Smoky Mountains. Good for you. That means it’s time to visit some of America’s lesser-known national parks—places that draw smaller crowds but are equally astounding. At these hidden gems, from Alaska to South Carolina, you’ll hike through watery caves, examine ancient cliff dwellings, and ride a bush plane to Arctic sand dunes.