Katmai national park, Alaska

Katmai, in southern Alaska, is for the bears: it’s home to the world’s largest population of Alaskan brown bears, a subspecies of the grizzly. Over 2,000 bears live in Katmai and thanks to their salmon-rich diet, they are some of the largest bears in the world, with mature males routinely reaching over 1,000 pounds (453kg), more than twice the size of the average Yellowstone grizzly. With the backcountry full of bears, people usually stay within a small section of the four-million-acre park. The most popular area is Brooks Camp, at the mouth of the Brooks river, on the shore of Nanak lake.

Here hundreds of bears congregate in summer and autumn to feast on salmon, which pass through in July and September on their seasonal breeding migrations. From June to September, visitors can view the bears from wooden platforms along the river. Katmai national park is also home to some of the most active volcanoes in the world. The Valley of Ten Thousand Smokes is an ash-filled valley devastated by the largest volcanic eruption in the 20th century, which took place in June of 1912, when Mount Katmai and Novarupta erupted simultaneously, expelling an estimated 13-15 cubic kilometres of ash.

Top tip After viewing the brown bear feast at Brooks Camp, board one of the park buses for a tour through the Valley of Ten Thousand Smokes. More than 100 years since the 1912 eruption, the smoking fumaroles are quiet, but creeks and rivers have carved canyons into the ash hundreds of feet deep and only a few feet wide, giving visitors a dramatic glimpse into the geologic layers of the eruption.
• Park website

Gates of the Arctic national park and preserve, Alaska

Sitting above the Arctic Circle, Gates of the Arctic is the most northerly US national park and its second-largest, being slightly bigger than Belgium. With no roads and little development, the park tends to attract only the hardiest and most adventurous of travellers. The stunning, glacier-carved Brooks Range straddles the park, running east to west, along the Continental Divide. Water running down the southern slopes of the range flows to the Pacific, while water running off the northern side flows to the Arctic Ocean.

Access is by way of the Dalton Highway, a primitive, sometimes unpaved road that runs from Fairbanks up to Prudhoe Bay on the Arctic Ocean, skimming the eastern border of the park. Entrance from the road means crossing the deep, cold, fast waters of the Middle Fork of the Koyukuk river without a bridge. Because of this natural barrier, most visitors are content with viewing the park from the road, on their way north.

More determined visitors can arrange to be dropped off on one of the park’s many lakes by a small seaplane. Another option is to fly to the airstrip at Anaktuvuk Pass, a Nunamiut village in the north-east of the park, home to around 350 people. Anaktuvuk Pass boasts the most remote post office in the US and its Simon Paneak Memorial Museum celebrates Nunamiut culture and displays artefacts related to the tribe’s history of semi-nomadic caribou hunting.

Top tip The best strategy is to start at the park headquarters in Fairbanks and drive to the ranger station in Bettles, just south of the park. From there you can arrange for a plane to drop you off in the backcountry. Be sure to arrange for pick-up before your supplies run out. Summers are short and snowstorms can sweep in any month of the year.
• Park website

North Cascades national park, Washington state

Most of the least-visited parks are remote and hard to reach. But North Cascades is within 100 miles of Seattle and yet, in 2015 it had just under 27,000 visitors. The low numbers are probably due to limited road access. Highway 20 bisects it at Ross Lake, but the park, most of which is within the Stephen Mather Wilderness, has few other maintained roads.

However, the lack of roads is part of what makes North Cascades special: this rugged expanse is virtually untouched, extending north into Canada, where it becomes the Skagit Valley provincial park. The promise of native wilderness lures experienced backpackers and mountaineers, who tramp the 18 miles of the Pacific Crest Trail that run through the park and seek out North Cascades’ remote peaks, which have names like Mount Terror and Inspiration Peak.

Most visitors come to Ross Lake national recreation area, a 12,000-acre manmade reservoir that bisects the park and provides power to Seattle through a series of hydroelectric dams. Fishing, canoeing, camping and kayaking are popular.

Top tip Cascade Pass was once an important trade route for Native Americans travelling between the coast and the interior. To retrace their historic footsteps, leave from the town of Marblemount and drive to the end of the Cascade river road. From there hike a moderate 3½ miles to the pass, which at 1,643 metres is above the tree line, affording spectacular views.
• Park website

Great Basin national park, Nevada

Highway 50, running east to west through central Nevada’s high desert, is nicknamed the Loneliest Road in America. So it’s no surprise that one of the country’s least-visited national parks lies along this road.

Great Basin, in eastern Nevada, protects a small pocket of this state’s famous “basin and range” topography – created by deep-rooted forces pulling apart the continental crust, forming a series of parallel basins and mountain ranges across the state. Great Basin national park near the town of Baker, was created in part to protect a stand of bristlecone pine trees that are among the oldest living organisms on Earth, up to 5,000 years old.

Key sights are Wheeler Peak, at 3,982 metres the second-tallest mountain in Nevada, and the Lehman caves, a complex of deep caverns known for their beautiful flowstone formations of stalactites, stalagmites, and helictites. Tours are offered several times a day by park rangers, covering the geology, ecology and history of the caves. The park also has two campsites and is known for its exceptionally dark night skies, perfect for stargazing.

Top tip The Grand Palace cave tour is 90 minutes long and explores underground treasures such as the Gothic Palace, the Music Room, the Lodge Room, Inscription Room, and the Grand Palace sections of Lehman Caves.
• Park website

Black Canyon of the Gunnison national park, Colorado

This is not the deepest canyon in North America but it is the steepest, with the Gunnison river falling more than 10 metres per mile as it plunges through this narrow national park in south-west Colorado (in comparison, the Colorado river drops an average of 2.3 metres per mile through the Grand Canyon).

The name refers to the limited sunlight that reaches its depths, which are made even darker by the black Precambrian gneiss and schist rock of the canyon walls. This 1.7-billion-year-old rock is extremely hard and good for rock climbing, though scaling the steep, sheer walls should only be attempted by experts.

Hiking from the rim into the canyon is not for the faint of heart, either. A number of routes descend from north and south rims, but the trails are unmarked and unmaintained, requiring route finding and Class 3 scrambling skills. Poison ivy also grows abundantly in the canyon, deterring even the most agile hikers.

Top tip The best views of the Black Canyon of the Gunnison are from Exclamation Point, an easy-to-moderate three-mile round trip hike on the north rim that leads to an overlook.
• Park website

Organ Pipe Cactus national monument, Arizona

This slice of the Sonoran desert biome is a vibrant desert habitat and the only place where the rare and stunning organ pipe cactus grows wild. Pollinated primarily by bats, this cactus has the heft and presence of the iconic saguaro cactus, but with many more arms snaking upwards from its central trunk. Many other species of cactus and plant also thrive here, with flowering cactuses making for stunning spring colours.

One reason visitor numbers are low is because the park is on the border with Mexico, where drug smuggling and immigration issues are rampant. Incidents involving visitors are rare, but people are advised to stay on marked trails, not pick up hitchhikers and report suspicious activities to rangers or border patrol agents. The park has two campsites, one for RVs, the other for tents only.

Top tip Drive or cycle the 21-mile Ajo Mountain drive to the Arch Canyon trailhead. From here an easy 1.2-mile roundtrip trail leads to views of a 25-metre wide natural arch.
• Park website

Isle Royale national park, Michigan

At 45 miles long and nine wide, Isle Royale is the largest island in Lake Superior. That hardly seems enough room to support several hundred moose and a few dozen wolves, yet this island is home to one of the most thoroughly studied predator-prey interactions in the world.

Since 1980, the animals have been tracked by biologists interested in how the rise and fall of moose on the island impacts the number of wolves. In harsh winters, the moose population dwindles to a few hundred, with the wolves dropping to around a dozen. In lush summers, as many as 1,000 moose and three dozen wolves have been counted. The island is considered a closed population, but both animals have been known to come and go, swimming across Lake Superior or crossing on the ice in winter.

With such a rare and delicate predator-prey dynamic, the number of human visitors is limited. Wolves are shy: sightings are rare and interactions rarer. In the north-west corner of Lake Superior, the island can only be reached by boat or seaplane. Seasonal ferries operated by the national park service run from Houghton and Copper Harbor, Michigan, and Grand Portage, Minnesota. Camping is allowed in 36 backcountry sites, reachable by foot or boat. No vehicles are allowed on the island.

Top tip For a true wilderness backpacking experience, hike the Greenstone Ridge Trail, which runs for 40 miles from one end of the island to the other. It usually takes four to five days and hikers can arrange to be picked up by shuttle boat at the other end of the island.
• Park website

Congaree national park, South Carolina

Deep in the swamps of southern South Carolina is one of the largest intact stands of old-growth hardwood trees in North America. In the late 1960s, private landowners were considering selling off tracts for timber development until the Sierra Club campaigned to have over 20,000 acres just south-east of Columbia declared a national monument in 1976. In 2003, the area was upgraded to national park status.

The trees in Congaree are some of the tallest hardwoods in the world and the park is nicknamed the Redwoods of the East. The canopy height averages 30 metres and the park is home to at least 15 “champion trees”, a title bestowed on the tallest known specimens of a species. These include a 49-metre sweet gum, a 47-metre cherry bark oak, a 41-metre American elm and a 38-metre laurel oak. These trees stand in a swampy flood plain forest that floods a few times of year.

Because much of Congaree is swampy, the best way to explore it is by canoe. The Congaree River Blue Trail starts in the state capital, Columbia, and runs for 50 miles downstream. Paddlers may catch a glimpse of the park’s abundant wildlife, including bobcats, river otters and a variety of bird species, many of which are unique to this forest.

Top tip Visitors can walk through the Congaree swamp without getting their feet wet on the 2.4-mile elevated Boardwalk Loop starting from the Harry Hampton Visitor Center in the north of the park.
• Park website

Dry Tortugas national park, Florida

One way to keep a park from being overrun by visitors is to make it accessible only by boat. Dry Tortugas is 68 miles off the main Florida Keys. Named for an abundance of turtles (tortugas in Spanish) and lack of potable surface water, these westernmost and most isolated of the Keys have healthy populations of birds and sea turtles, who see only around 60,000 people a year.

Dry Tortugas may belong to the turtles, but it’s dominated by Fort Jefferson, a massive but unfinished fortress built in the late 1800. The fort is the largest masonry building in the western hemisphere and the cost of building and maintaining it in the face of hurricanes and harsh salty conditions could not be justified for long. After being used as a prison and medical quarantine facility, it was turned into a National Monument in 1935 and a national park in 1992.

Dry Tortugas is reached by ferry, boat or seaplane from Key West. Most people come to snorkel or dive in the clear blue waters around the thriving coral reefs. Others come with food, water and supplies to camp under the stars in the primitive campsite near the fort.

Top tip In April and May, migrating sea birds fly over Dry Tortugas, often landing for a rest on the island. Species counts during these flyovers are legendary, with 100 or more species sometimes spotted in a single day.
• Park website

National Park of American Samoa

This park, in the South Pacific, nearly 5,000 miles from the California coast, has long been a strategic military outpost for the US. Three of the islands – Tutuila, Ofy and Ta’u – were declared a national park in 1988. Only around 10,000 visitors make their way here each year.

American Samoa is made up of overlapping shield volcanoes erupted from an underwater hot spot that has been active for at least 1.5 million years. As the Pacific plate moved over this hot spot, it created an island chain, much like the islands of Hawaii. The volcanoes are not currently erupting, but are still considered active. Periodic collapses of parts of the shield volcanoes can set off tsunamis and leave behind sea cliff scars over 900 metres high, forming some of the highest sea cliff escarpments in the world.

Visitors come to American Samoa mainly for snorkelling and whale watching. The waters are rich in marine life, including sea turtles, humpback whales, over 900 species of fish and 250 species of coral. Some of the largest living coral colonies are found in the waters around Ta’u Island.

Top tip The Samoan culture is one of the oldest in Polynesia and still thriving on American Samoa. The park operates a homestay programme, where visitors can stay in a traditional village, eat home-cooked food and participate in customs and crafts, such as ceremonial mat-weaving.
• Park website

Mary Caperton Morton is a freelance science and travel writer based in Big Sky, Montana. Follow her travels at theblondecoyote.com