Toroweap Overlook Grand Canyon National Park, Arizona Photo by Ken Lund / Flickr (use permitted with attribution/share alike).
Grand Canyon National Park
The National Park Service protects the wonder and majesty of the Grand Canyon, whose size alone is overwhelming; 277 river miles long, up to 18 miles wide, and a mile deep! Laid bare in the rocks of the Grand Canyon are the last two billion years of Earth's history.