1. Olympic National Park, Washington State

When: Open year round but some facilities have reduced hours from October to May.

Why: If you’re seeking solitude, you’re in the right place. The Hoh Rain Forest is one of the park’s most popular attractions because of its moss-cloaked floor and thick canopy of spruce, cedar, fir and hemlock trees. It’s also famous for being incredibly quiet. The pristine park’s high ecological value has earned it International Biosphere Reserve and World Heritage status. When it comes to exploring this ancient wilderness, you can hike, surf, paddleboard, kayak, fish or simply enjoy watching the resident black bears and elk.

stateofwatourism.com

2. Yellowstone National Park, Wyoming

When: In winter, for a unique Wild West experience.

Why: You can’t do a tour of America’s national parks without exploring one of the most famous. Yellowstone – or Jellystone, for a particular generation – draws travellers year round to see abundant wildlife and active geysers, and to go hiking and fishing. Summer is busy, so head here in the off-season. Most of the roads are closed to cars in winter (except the North Entrance, in Montana), however you can still enter the park in the south, east or west on a snowmobile or snow coach tour, or on snowshoes and cross-country skis. As for wildlife, expect to see bison and elk.

travelwyoming.com

3. Mesa Verde National Park, Colorado

When: Mid-May to late October for cliff-dwelling tours.

Why: Mesa Verde is famous for its Ancestral Puebloan cliff dwellings – rooms built into sandstone alcoves between 1190 and 1280. There are 600 of them in the park, the largest of which (and largest in North America) has been dubbed Cliff Palace; it features 150 rooms and is thought to have housed about 100 people. Native Americans lived in these homes built of sandstone, mortar, wood and stone for nearly a century, before migrating south. However, these fascinating “villages” remain, and you can visit them on tours with park rangers, accessing sites via ladders. Mesa Verde is also an International Dark Sky Park, making it great for astrophotography.

colorado.com

4. Hawai’i Volcanoes National Park, Hawai’i

When: Midweek during shoulder seasons. Avoid the Christmas-New Year period.

Why: Hawai’i is more than world-class beaches and Jurassic-like forest. There’s also Hawai’i Volcanoes National Park, on the island of Hawai’i. The park has two of the most active volcanoes in the world and, yes, one of them, Kīlauea, was erupting at the start of the year. But it’s now stopped and the park has reopened and is safe, with hikers instructed to stay on marked trails. Although the park is big and popular, lesser known is the Kahuku Unit, located on the “shoulders” of the second volcano, Mauna Loa. The area offers a tonne of hiking, including to Nāhuku, where you’ll explore a rainforest before reaching a 500-year-old lava tube.

gohawaii.com

5. Biscayne National Park, Florida

When: Any time outside hurricane season in June to late November.

Why: Leave the forests behind and head under water to explore Biscayne’s fascinating shipwreck history. Follow the park’s Maritime Heritage Trail to six wrecks (marked by buoys), which you can reach by scuba-diving or snorkelling. The newest addition to the trail is the very cool and kind of spooky Fowey Rocks Lighthouse, which was built in 1878 and protrudes from the sea. The park is 95 per cent water, so expect to discover its coral reefs and mangrove forests via kayak or fishing boat, or on a guided tour.

miamiandbeaches.com

6. Badlands National Park, South Dakota

When: Summer gets thunderstorms, so visit in spring and autumn.

Why: Scientists have uncovered 19,000 fossils at a site called the Big Pig Dig, one of Badlands’ most popular attractions. Those fossils belong to ancient giant pigs (Archaeotherium), hence the site’s name, hornless rhinos (Subhyracodon) and small horses (Mesohippus). Other fascinating finds have been fossils of the mosasaur, a marine lizard that was an apex predator. You can learn more about these ancient creatures and meet a palaeontologist at the Fossil Preparation Lab (open June to September). If you’re travelling with young kids, head out on the Fossil Exhibit Trail, a short wander along a boardwalk with fossil replicas and exhibits.

travelsouthdakota.com

7. Wrangell-St Elias National Park, Alaska

When: August – there are fewer mosquitoes and snow is yet to fall.

Why: The largest park in the US at more than 5 million hectares, this Alaskan Goliath has the whopping Malaspina Glacier, some of the country’s highest mountains, and a former copper-mining boomtown. Photographers and history buffs will love the decaying red timber buildings of Kennecott Mines National Historic Landmark. You can go inside Kennecott Mill on a guided tour in summer. Other reasons to venture here include ice-climbing and hiking.

travelalaska.com

8. Capitol Reef National Park, Utah

When: Open year round but spring and autumn have the best weather.

Why: Capitol Reef is Utah’s least-known park, which means fewer tourists and an experience your mates probably don’t know about yet. Despite flying under the radar, it has stunning cliffs, slot canyons and natural bridges, as well as petroglyphs. The engraved rock etchings tell the hunting, crop-growing and belief stories of the Native American Fremont and Ancestral Puebloan people who lived here from about AD600-1300. There’s also the cool new Skyview Hotel, just outside the park, in Torrey. The sleek property has a rooftop terrace that makes for a sublime stargazing experience in what is Utah’s first International Dark Sky Community. While there, enjoy a traditional American pie at historic Gifford Homestead, and pop into the neighbouring Mormon settlement of Fruita. 

visitutah.com

9. Redwood National Park, California

When: Spring, when there are fewer people and the forest is lush.

Why: Who can resist staring up the trunks of the tallest trees in the world? Redwood is famous for its old-growth forest, with some trees soaring to 112m. Combined with state parks to form the Redwood National and State Park system, this International Biosphere Reserve is great for wildlife watching – elk, deer, whales, seals – as well as pretty wildflowers. Spend a few nights at one of the RV-friendly campgrounds, such as Jedediah Smith Campground, where you can sleep under the trees near a river. Local’s tip: Reserve a campsite six months before arriving.

visitredwoods.com

10. Hot Springs National Park, Arkansas

When: Although summer is humid, the rest of the year is wet or snowy.

Why: As its name suggests, this national park’s biggest drawcard is its thermal water. Although you can’t swim in the springs within the park, the water is piped into two bathhouses on none other than Bathhouse Row in the town of Hot Springs. You can also drink the thermal water from several fountains throughout town. In the park itself, there are two pools where the water has cooled enough for you to touch: Hot Water Cascade and the Display Springs. There is also hiking and camping.

arkansas.com

See also: 

Only in America: 10 incredible US stays

5 USA road trip rules you need to know

20 things Aussies get wrong in the USA