7 of the most unique national parks in the US, according to someone who's been to all 50 states

South Carolina’s Congaree National Park is home to one of the country's largest expanses of old-growth forest.

Although some would be tempted to call it a swamp, it’s a floodplain, meaning the water that floods the area eventually dries up before flooding again.

When the forest floor is dry, you can walk through it. But the park is best explored from a kayak or canoe when it floods.

Whether the park is flooded or not, some of the best views of the park’s enormous loblolly pine trees (many over 100 feet tall) can be viewed from the 2.6-mile looped boardwalk trail.

The park is free to visit and open year-round, but because this is South Carolina, expect heat, humidity, and mosquitos in the summer.

Unsurprisingly, fall, winter, and spring are the best time to visit.

Like Congaree, Voyageurs National Park is fee-free year-round, and it’s also one of the least-visited national parks.

Because most of this park consists of water, the best way to explore it is by boat, kayak, canoe, or other watercraft. Come winter, the water freezes, and snowmobiles replace boats.

In fact, there are over 100 miles of snowmobiling trails on the park’s main island, and locals are even known to drive their trucks over the ice to go sledding.

Because it’s so far north and the skies are so dark, it’s one of the best places to see the Northern Lights within the contiguous 48 states.

There are so many ways to explore Wyoming’s Grand Teton National Park.

Not only can you drive into and around the park, but also you can bike from nearby Jackson Hole along a protected bike path right into the park.

In warm weather, hiking and biking are the best ways to make your way through the park — and you can also catch a boat across famous-for-a-reason Jenny Lake. Come winter, you can snowshoe and cross-country ski if the snow is too deep to hike.

The park is also a great place for seeing animals like bears, moose, and elk.

Yellowstone National Park's mountains, valleys, canyons, rivers, lakes, trails, and rugged wilderness are breathtakingly beautiful, and you won’t find as many thermal features so densely concentrated anywhere else in the world.

In some cases, you’ll even find all four — mud pots, geysers, hot springs, and steam vents — easily accessible at a single geyser basin.

If you hate crowds (and the lines of backed-up cars accompanying them), avoid this park in the summer. Consider visiting during the winter, when the cold air makes the geyser steam more visible.

California has more national parks than any other state (nine total), but one of the most special is Channel Islands National Park.

Sometimes referred to as the “Galapagos of North America,” the park has loads of animals, including 145 species you won’t find anywhere else.

Plus, visitors can scuba dive to explore the park. Seeing the park from below the water is an experience like no other, and you’ll have a greater chance of spotting some of the park’s 2,000 species of flora and fauna if you go above and below the water.

Saguaro National Park has sections on both sides of Tucson, meaning the city is basically inside the national park.

The proximity to the city means having easy access to various accommodations, loads of dining, evening entertainment, and activity options.

It's easy to make a quick day trip to Saguaro — it’s about a two-hour drive from Phoenix, and just a 30-minute drive from the Tucson airport.

When you arrive, you'll see where the park got its name: Endless miles of thousands of saguaro cacti populate the desert, lining trails that make their way up to mountaintops.

Saguaro National Park’s more popular neighbor to the north is the world-famous Grand Canyon National Park.

If you can’t hike all the way down the popular Bright Angel Trail, try the 14-mile rim trail that traces the southern rim of the canyon.

Most of the trail is flat and paved, and there are shuttle buses running along the route so you can get dropped off at one end and make your way back.

Though many people only see the park from the lookout point at the main visitor center, the most special way to experience the park is by river rafting it.

It's a way to see the canyon from the bottom up. Plus, it's the only way to access most of the slot canyons, waterfalls, rocky overlooks, hidden oases, and Native American sites scattered across hundreds of miles of river.