There’s a reason few people visit California’s equivalent to the Galapagos Islands of South America: It’s only accessible by boat or a short flight. But, once you step foot on one of the five islands that make up Channel Islands National Park, you’ll discover dozens plant and animal species that can’t be found anywhere else in the world. Spend your time here hiking, snorkeling, kayaking, or bird watching. 

Most people think of Redwood National and State Parks when they hear “big trees,” but Congaree National Park is just as impressive. It's nicknamed the “Home of Champions,” and it's not as congested with tourists as its Californian counterpart. Here, you can hike more than 25 miles of forested trails, fish the waterways, or explore the marked canoe trail on Cedar Creek. A boardwalk provides access to scenic Weston Lake.

While it’s not the Grand Canyon, the Black Canyon is definitely breathtaking. Its 2,000-foot walls drop almost vertically to the Gunnison River and, at their narrowest point, span only 40 feet across. You can hike, fish, kayak, raft, or rock climb here. 

The cave itself isn’t necessarily overlooked, but the above-ground Wind Cave National Park – a sea of prairie grass dotted with bison – is. It's also one of the nation's few remaining intact prairies. Here, you'll find 30 miles of hiking trails as well as horseback riding and camping. Just as they do at Carlsbad Caverns National Park or Mammoth Cave National Park, tickets for the cave tour sell out fast, so be sure to book early. 

Thanks to its remote location along the Canadian border, Voyageurs National Park never gets too crowded. During summer months, you can enjoy fishing, boating, and other water-based activities. On land watch for moose, gray wolves, black bears, beavers, bald eagles, and wolves. You might even see the Aurora Borealis at night if you're lucky. The park remains open during the winter months for cross-country skiing, snowshoeing, ice fishing, and snowmobiling.

Co-managed by the National Park Service and the Navajo Nation, Canyon de Chelly is often bypassed in favor of the Grand Canyon (which is located 250 miles west)  and nearby Monument Valley. Here, you'll find vantage points from the rim overlook Navajo farms, Ancestral Pueblo ruins, and sacred rock formations. Pro tip: Find a Navajo guide to see petroglyphs and more ruins from the canyon’s interior.

A trip to National Park of American Samoa requires a five-hour flight from Honolulu to Tutuila Island, which is part of the United States territory of American Samoa. The long commute is worth it, though. Here, visitors can hike through tropical rainforests, snorkel over coral reefs, or just relax on the beach. The park also offers a homestay program that places visitors with Samoan families. 

Located 150 miles south of Mesa Verde National Park, this Ancestral Puebloan community is a UNESCO World Heritage Site. A nine-mile paved loop accesses five major Chacoan sites, including Pueblo Bonito, a magnificent house that once stood four stories high and had more than 600 rooms. The drawback to a visit here is that the park is very remote and offers minimal services.

You don’t have to worry about jam-packed parking lots at Isle Royale. The rugged island is surrounded by Lake Superior, and can only be accessed by boat or seaplane. Here, you can hike, canoe, or scuba dive to well-preserved shipwrecks. A word of warning: Although the park receives fewer visitors annually than Yellowstone does in a day, the park’s per-acre use is among the highest in the national park system.

Named for two mountain ranges that form its backbone, this park is America’s largest. In fact, you could fit Vermont and New Hampshire combined – or the entire country of Switzerland – within its borders. But, it's also one of the least visited, bypassed in favor of Denali National Park. You can do many of the same activities at this overlooked park (think: hiking, biking, fishing, and more), with fewer people around.