As we celebrate the 100th anniversary of the creation of the National Park Service and its mission to “conserve the scenery…unimpaired for the enjoyment of future generations,” it’s important to remember that all national parks and monuments are worth defending—large and small, urban and wild, accessible and remote.

Earthjustice works to preserve the natural beauty and cultural significance of America’s parks. We fight for strict government regulation of haze pollution from power plants, greater legal protections for endangered species and a reduction in the hazardous greenhouse gasses that drive climate change. And we know that our shared history is equally worth protecting for everyone, everywhere to enjoy.

Here are six of our nation’s hidden gems:

1. Maryland: Fort Washington

Shortly after the Revolutionary War, Congress created a system of forts to protect America’s important ports, and General George Washington suggested locating one on the east bank of the Potomac River. During the War of 1812, under threat from the British, Fort Warburton—later renamed Fort Washington—was destroyed by U.S. troops. The fort was rebuilt by 1824 and stood as the only defense of the nation’s capital, Washington, D.C., until the Civil War.

Fort Washington became a national park in 1946. Today, park visitors can birdwatch, fish in the Potomac River and watch Civil War artillery demonstrations by costumed docents. The public can also visit the Fort Washington Light, a lighthouse built on the site in 1857 and tended by hand until 1954.

2. Arizona: Montezuma Castle National Monument

Montezuma Castle was one of the first sites in the U.S. to be declared a national monument. President Teddy Roosevelt dedicated this site along Beaver Creek in 1906. Despite its name, Montezuma Castle is neither a castle nor was it built by the Aztec ruler Montezuma, who was born decades after the site was abandoned. The “castle” is actually a series of carved dwellings high in the limestone cliffs occupied by the Sinagua Native Americans from 1200 to 1450 AD.

Until 1951, visitors were allowed to climb ladders into the ancient cliff houses, much as the Sinagua once did. But like feeding the grizzly bears of Yellowstone, this park tradition was phased out for reasons of preservation and personal safety. Still, more than 350,000 visitors come to see the prehistoric ruins every year and learn about the history of Native American settlement in the Southwest.

3. California: Pinnacles National Park

Pinnacles National Monument was established by Teddy Roosevelt in 1908; in 2013 President Obama declared the site our country’s newest national park. The park’s caves and crags were formed by lava from volcanic eruptions that occurred 23 million years ago. This “field of fire” was then split down the middle by the San Andreas Fault. The result of the geological upheaval is towering rock spires that climbers love, alongside talus caves, formed when fissures in the rock filled with gigantic boulders that fell from above.

About 250,000 people visit Pinnacles each year to take in the park’s stunning landscapes and wealth of biodiversity. The park is home to rare Townsend big-eared bats, red-legged frogs and California condors, as well as 400 species of bees—the greatest diversity of bees found anywhere on Earth.

4. Michigan: Isle Royale National Park

Bobbing in Lake Superior, the world’s largest freshwater lake, are one large island and more than 450 smaller islands known as Isle Royale. The national park was created in 1940 and was designated an International Biosphere Reserve in 1980. The park is only accessible by boat and seaplane, and just 18,500 intrepid trekkers visited in 2015. Adventure-seekers can Scuba dive into Lake Superior to see the largest collection of intact shipwrecks in the national park system.

The scientific study of wolves and moose living on Isle Royal is the longest running predator-prey study in the world, begun in 1958. In recent years, moose populations have skyrocketed while wolf numbers have fallen due to inbreeding; just two wolves remained in 2015. Sadly, despite pressure from Earthjustice and our partners, the National Park service is still debating whether to introduce new wolves to the park or let the pack die out.

5. Oregon and Washington: Columbia River Gorge National Scenic Area

Though not technically a national park—the site is administered by the U.S. Forest Service and local agencies—the Columbia River Gorge National Scenic Area protects a magnificent 85-mile-long, 4,000-foot-deep canyon that is the only sea level route through the Cascade Mountains. President Ronald Reagan signed an act creating the 292,500-acre scenic area in 1986.

The western part of the gorge is a place of rainforests and waterfalls, while the eastern part features rolling hills and rich farmland. The gorge is known for its unspoiled scenery and a 10,000-year history of human habitation. Earthjustice is fighting to keep the Columbia River Gorge from becoming the site of the largest crude oil terminal on the West Coast. The terminal would handle 360,000 barrels of oil a day, brought through the gorge by train, exposing the scenic area to the risk of catastrophic oil spills.

6. American Samoa: National Park of American Samoa

Twenty-six hundred miles southwest of Hawai‘i lies America’s most remote national park and the first in the Southern Hemisphere. The National Park of American Samoa includes parts of the rain forested, volcanic islands of Tutuila, Ta‘ū and Ofu, as well as about 4,000 acres of undersea land. The area was leased by the National Park Service in 1993 from Samoan chiefs and is still jointly administered by the Samoan people, some of whom practice subsistence farming in the park.

The park is home to many rare and threatened animals, including giant flying foxes—fruit bats with a three-foot wingspan. The majestic coral reefs that ring the islands are teeming with sea turtles, humpback whales, 250 species of coral and 950 species of fish.

Additional reporting by Diana Tarrazo

As the National Park Service turns 100 this summer, the 100 Years Wild series celebrates the value of public lands as refuges to wildlife and people, while also shining a light on the threats to these irreplaceable landscapes in a changing and warming world.