White Sands National Monument, New Mexico The first thing you’ll notice is that the name is actually a bit of a misnomer. The sand is beyond white—it’s practically silver. Second, even in the searing afternoon sun, it doesn’t get hot. That’s because it’s gypsum sand: The New Mexico park is the largest gypsum dune field in the world. Take advantage by renting a saucer from the visitor center and sledding your way down.
Padre Island National Seashore, Texas The dunes here serve as a nesting ground for the critically endangered Kemp’s ridley sea turtles. Head to Malaquite Beach from mid-June through August to watch the hatchlings scurry into the Gulf of Mexico.
Vanderbilt Mansion National Historic Site, New York Its Beaux-Arts architecture is a premier example of Gilded Age opulence, but the sweeping views of New York’s Hudson Valley are equally indulgent. The mansion comes to life at Christmas, while summer is ideal for ambling through the acres of lavish gardens.
First Ladies National Historic Site, Ohio Tucked into the childhood home of Ida Saxton McKinley, the museum is the country’s most complete tribute to presidential spouses, from Martha Washington to Michelle Obama.
Castillo de San Marcos National Monument, Florida The oldest masonry fort in the continental U.S. (above) was completed in 1695 by the Spanish using coquina, a sedimentary rock made almost entirely of seashells.
Touro Synagogue National Historic Site, Rhode Island The oldest synagogue in the country was born from a classic American tale: The congregation was founded in 1658 by descendants of Jewish families who fled the Spanish and Portuguese inquisitions, crossed the Atlantic to Barbados, and eventually found freedom from persecution in Rhode Island. Every August, congregants gather for a reading of a 1790 letter on religious freedom from George Washington to the Hebrew congregations of Newport.
Salmon Cascades, Olympic National Park, Washington Late every summer, resplendent coho salmon race up the Sol Duc River to spawn their young. Watch the drama in real time as they writhe and flip their way up these tempestuous falls.
Various falls, Shenandoah National Park, Virginia The 93-foot Overall Run waterfall and the cliff-jumpable White Oak Falls may compete for most dramatic feature, but venture past both on the Cedar Run Trail for a secluded natural water slide. Plan to go at the height of summer: The water can be cool.
Little Niagara, Chickasaw National Recreation Area, Oklahoma The frigid, spring-fed waters of Travertine Creek spill over short falls that are perfect for young swimmers and adventurous teens alike.
Guadalupe Mountains National Park, Texas Fear not for El Capitan (above), which rises like a Stetson from the Chihuahuan Desert. Though daunting at first glance, the path to the top “is difficult but not beyond the ability of any two-legged American, aged 8 to 80, in normal health,” wrote famed Western writer Edward Abbey in Beyond the Wall. Once at the summit, revel in the fact that you’re standing atop a 280-million-year-old limestone barrier reef.
Capulin Volcano National Monument, New Mexico From this 8,182-foot peak, take in panoramic vistas of four states and more than 100 smaller volcanoes. Don’t worry: They’ve been dormant for at least 30,000 years.
Painted Cave, Channel Islands National Park, California Kayak through one of the largest and deepest sea caves in the world (above), which gets its name from the radiant lichens and algae decorating the entrance.
Oregon Caves National Monument and Preserve, Oregon In the fall of 1874, while tracking a bear in the Siskiyou Mountains, Elijah Davidson inadvertently discovered what came to be known the “Marble Halls of Oregon,” unique because cave systems are typically carved from limestone or dolomite.
Gila Cliff Dwellings National Monument, New Mexico For thousands of years, nomadic people huddled in caves perched alongside the Gila River for temporary shelter. The Mogollon people made a permanent home there in the 1200s, creating striking cliffside dwellings that endure despite the harsh desert climate.
Russell Cave National Monument, Alabama An important refuge for the winter survival of American Indian tribes for more than 10,000 years, the cave provides one of the most thorough archaeological records of prehistoric culture in the southeastern U.S.
Endless Wall Trail, New River Gorge National River, West Virginia Trek through hemlocks and rhododendron thickets to reach Diamond Point, nearly 1,000 feet above the river, and listen for the whitewater raging far below. Then, book a raft tour for an up-close encounter.
Oakridge Trail, Congaree National Park, South Carolina This lesser-trod trail offers the chance to take in majestic old-growth trees in solitude—as long as you don’t count the armadillos, wild hogs, skinks, skunks, southern flying squirrels, alligators, and bobcats. Be sure to check the “Mosquito Meter” for more potential companions: It ranges from “all clear” to “war zone.”