The park includes more than a million acres of land. The Colorado River travels for 277 miles through the canyon from Lees Ferry to the Grand Wash Cliffs. At the South Rim, near Grand Canyon Village, it's a vertical mile -- about 5,000 feet -- from the rim to river or a 7-mile hike. The width of the canyon at Grand Canyon Village is 10 miles although in places it is as wide as 18 miles.
The Grand Canyon has two very different personalities.
Most visitors see the South Rim, the most-accessible part of the park that is open year round. Just 10 miles away as the crow flies is the vastly different North Rim. It's 1,000 feet higher, typically inaccessible from October to mid-May because of heavy snows and much more remote. They might only be 10 miles apart in the air, but driving between the two is a 220-mile trip. Or you can hike the 21 miles from rim to rim but that typically takes two the three days. (A rafting trip down the Colorado can take two weeks or longer.)
While the Grand Canyon is probably the world's most famous canyon, it is not the deepest. Barranca del Cobre in northern Mexico and Hell's Canyon in Idaho are both deeper. And those are just two examples.
The canyon was first afforded federal protection in 1893 as a Forest Reserve and later as a National Monument. But it wasn't until 1919 -- three years after the creation of the National Park Service -- that the Grand Canyon achieved National Park status.
That first year, 44,173 people visited the park. Today, nearly five million visitors a year come to gaze out at its beauty.
#4: Hawaii Volcanoes National Park If you want to get close to flowing lava -- and we mean real close -- this is the place to be. On Hawaii's Big Island, Hawaii Volcanoes National Park allows visitors to witness the destructive, yet creative power of nature first hand. Kilauea Volcano has erupted lava almost continuously from its east rift zone since 1983. These lava flows have added more than 568 acres of new land to the southern shore of Kilauea and covered 8.7 miles of highway with lava as deep as 115 feet.
At sunset, visitors carrying flashlights trek out to the end of the ocean to watch lava flow into the water. A few miles away, a crater that visitors could once hike through is now erupting for the first time since 1982, sending an ash-laden plume into the air. Elsewhere, visitors can hike through a hollowed-out tube that once carried lava.
The park highlights two of the world's most active volcanoes, and offers insights on the birth of the Hawaiian Islands and views of dramatic volcanic landscapes.
The current eruption of Kilauea has destroyed 187 structures including the park's Wahaula Visitors Center.
The current eruption rate of Kilauea volcano is 250,000-650,000 cubic yards a day. That is enough to resurface a 20-mile-long two-lane road every day. But remember, the eruption has been continuous since 1983. That would make the stack of lava on the road about 20 miles tall.
Be warned: visitors to the park, even returning ones, should always check in with the park staff to see what sites are open. Lava flow activity is always changing and you never know what's in store for your visit.