6) Grand Canyon National Park, Arizona
Arizona’s Grand Canyon National Park draws over five million visitors per year. Eager to see the canyon that was forged over millions of years by the Colorado River, most visitors go to the easily accessible South Rim which is open year-round. Only about 10 percent of visitors see the North Rim which closes in the winter and is a 220-mile drive from the South Rim. You can access the floor of the canyon by hiking, mule ride or rafting from upriver. It is also popular to camp on the floor where you’ll enjoy an amazing view of the night sky. This is recommended for any hikers trying to make the rim–to-rim journey. Changes in temperature, elevation and the physical exertion of the hike have forced park official to do perform many rescues for hikers unprepared for those elements. To avoid altitude sickness, it’s best to make the incline to the higher elevations gradually.