Celebrate the 100th birthday of America’s National Parks with these unforgettable experiences

As a travel writer who's explored national park sites across the U.S., I agree with author Wallace Stegner, who called these treasures the best idea America has ever had. In honor of this year's 100th anniversary of the National Park Service, here's my subjective list of best experiences in these natural and historical gems. The first three are in Iowa, while the rest will take you farther afield:

1. Take a hike at Effigy Mounds National Monument in northeast Iowa. The 2,526-acre property protects more than 200 gently rounded grass mounds - many in the shape of birds or bears - lining a high bluff overlooking the Mississippi River. Built approximately a thousand years ago, the ceremonial mounds are considered sacred by Native Americans. On a sunny autumn day, there's no more beautiful place to be than walking in the golden-leaved forest that surrounds the mounds.

2. Gain new insights into the only president born in Iowa at the Herbert Hoover National Historic Site in West Branch. Visit the two-room cottage where Hoover was born in 1874, then tour a museum that chronicles his achievements, which include organizing relief efforts during World War I that saved millions of Europeans from starvation. During his time in office, Hoover also expanded the land designated for new national parks and monuments by 40 percent.

3. In Sioux City, pay your respects at the Sergeant Floyd Monument, which honors the only member of the Lewis & Clark Expedition to die during the epic journey in 1804-06 that mapped the Louisiana Purchase. The Lewis & Clark National Historic Trail follows the Missouri River for much of Iowa's western border. In addition to the monument, it includes a full-size replica near Onawa of the keelboat used by the explorers and the Sioux City Lewis & Clark Interpretive Center, where you can view animatronic replicas of Lewis, Clark, and Lewis's dog Seaman, who barks when visitors approach.

4. Pitch your tent at Fruita Campground in Capitol Reef National Park in Utah, arguably the best campground in the entire National Park Service. This desert oasis is watered by the Fremont River, whose banks are shaded by lush groves of cottonwood, ash and tamarisk trees. An orchard planted by Mormon pioneers bears multiple varieties of fruits and nuts that can be enjoyed by campers, and there's a historic store serving freshly baked treats. Use the campground as a base for exploring the surrounding sandstone cliffs and canyons, richly colored and dramatically sculpted.

5. Go underground at Kentucky's Mammoth Cave National Park, the world's largest known cave system. Interconnected passageways wind for more than 400 miles. Admire the stalactites, stalagmites, and other formations created over millions of years, and learn about the cave's history as a tuberculosis sanitarium in the 19th century and the rare amphibians and crustaceans that live in its depths.

6. Be amazed at the bison herds in Theodore Roosevelt National Park in North Dakota. More than 300 of the great shaggy beasts make their home here, occasionally wandering through the campgrounds to add extra excitement to your visit. Nearly hunted to extinction by the late-19th century, they were saved in part through the efforts of Roosevelt, who came to this region in 1884 to rebuild his life after the deaths of his wife and mother. The park still is a place to rejuvenate one's spirit.

7. Explore the mysteries of an ancient civilization at Mesa Verde National Park in Colorado. The park has more than 4,500 archaeological sites left by the Ancestral Pueblo people, whose descendants include the Hopi of Arizona. These master builders constructed elaborate complexes tucked into sandstone cliffs. Some held just a few people, while others, such as the Cliff Palace and Long House, have 150 rooms and could have housed up to 100 people.

8. Walk the beach at Cape Hatteras National Seashore. Stretching for more than 70 miles along North Carolina's Outer Banks, this expanse of sand and salt marshes is also designated as a Globally Important Bird Area. More than 360 bird species can be seen here at various times of the year, including rare piping plovers, least terns and black skimmers. Then climb Bodie Island Lighthouse and Cape Hatteras Lighthouse for panoramic views of this landscape of water, sand, and sky.

9. Step into history at Gettysburg National Military Park. One of the most significant battles of the Civil War was fought in this rural part of Pennsylvania. Four months later, Abraham Lincoln delivered his famous address at the dedication of its military cemetery. Whether you're a Civil War buff or largely unfamiliar with the details of the conflict, Gettysburg will likely move you to tears with its stories of tragedy and heroism.

10. Admire in the scenery in Grand Teton National Park in Wyoming. Picking just one spectacular view in the National Parks is impossible, but certainly the appropriately named Cathedral Group in the Teton Range ranks on nearly everyone's short list. You'll find many stunning views of the range along Jenny Lake Scenic Drive.

National Parks by the Numbers

' Total amount of land protected by the NPS: 84 million acres in 409 sites.

' Most visited site in the NPS: Golden Gate National Recreation Area in San Francisco, which gets more than 15 million visitors a year.

' First national park in both the U.S. and the world: Yellowstone, which was established in 1872.

' Largest Site in the NPS: Wrangell-St. Elias National Park and Preserve in Alaska has 13.2 million acres.

' Smallest Site: Thaddeus Kosciuszko National Memorial in Pennsylvania has 0.02 acres.

' Number of miles of trails: 18,000

' Number of visitors to the 879 NPS visitor centers: 280 million

' For more information, see www.nps.gov.