Enjoy riverside camping in old-growth forest at Sol Duc, one of 15 developed campgrounds in Olympic National Park. To learn about each of these campgrounds and find out which ones accept reservations, click here.

Visitors can take a ranger-led 8.5-mile roundtrip hike over Red Basin, "a fossil-rich area part of the land within the 2004 boundary expansion of Petrified Forest National Park. Along this hike you will see petrified wood, petroglyphs, unique erosional formations such as hoodoos, vibrantly colored badlands deposited over 215 million years ago, and fossil clam beds."

National parks are great for all sorts of activities, from hiking to swimming to stargazing to horseback riding. At Yellowstone National Park, visitors can take a guided ride or bring their own private stock into the park. Click here for more information.

"Given its remote location and challenging weather conditions, Aniakchak is one of the most wild and least visited places in the National Park System. This landscape is a vibrant reminder of Alaska's location in the volcanically active "Ring of Fire," as it is home to an impressive six mile (10 km) wide, 2,500 ft (762 m) deep caldera formed during a massive volcanic eruption 3,500 years ago."

"Nearly 13,000 men died on these grounds, a site that became infamous even before the Civil War ended. Their burial grounds became Andersonville National Cemetery, where veterans continue to be buried today. This place, where tens of thousands suffered captivity so others could be free, is also home to the National Prisoner of War Museum and serves as a memorial to all American prisoners of war."

"An oasis in the desert, Amistad National Recreation Area consists of the US portion of the International Amistad Reservoir. Amistad, whose name comes from the Spanish word meaning friendship, is best known for excellent water-based recreation, camping, hiking, rock art viewing, and its rich cultural history. Amistad is also home to a wide variety of plant and animal life above and below the water."

"Photograph of a raised marine terrace (Qmt). The island, located near the mouth of the Douglas River, was cut flat by waves. Subsequently, it has risen approximately 15 m (50 ft). The foreground is a modern wave-cut platform that cuts across dipping beds of the Naknek Formation, Snug Harbor Siltstone Member."

"In the early 1900s, paleontologists unearthed the Age of Mammals when they found full skeletons of extinct Miocene mammals in the hills of Nebraska -- species previously only known through fragments. At the same time, an age of friendship began between rancher James Cook and Chief Red Cloud of the Lakota. These two unprecedented events are preserved and protected here... at Agate Fossil Beds."

"Over 200,000 African-American soldiers and sailors served in the U.S. Army and Navy during the Civil War. Their service helped to end the war and free over four million slaves. The African American Civil War Memorial honors their service and sacrifice."

"Kentucky was the 15th state to join the United States of America on June 1, 1792. It was not long after that Abraham Lincoln lived here at the Knob Creek Farm."