Route 66 - Grand Canyon

The site of the Grand Canyon is so overwhelming that it is no surprise that the Pueblo Native American population used to view it as a holy site and made pilgrimages there. The valley displays around two billion years of geology in the exposed rock walls of the canyon, with the site thought to have its origins around 17 million years ago. However, several credible scientific arguments say it is anything between six and 70 million years old.

In terms of human occupation, there is some debate as to when a distinct group with their own culture emerged, but there is considerable evidence to suggest that the ancient Puebloan people, referred to as the Anasazi ('Ancient Ones' in Navajo) who lived there around 3200 years ago are the ancestors of today's modern Pueblo-identifying population.

By the time the Europeans arrived in the mid-16th century, there was a complex society of many different tribes, co-existing and frequently intermarrying. The Spanish didn't have it easy in 1540 - their Hopi guides could likely have found them an easy route to the canyon floor, but the apparent difficulty meant that no European bothered with the canyon again for over 200 years.

The Grand Canyon is a U.S. National Monument, with Theodore Roosevelt - a conservationist and President - to thank for it. After a 1903 visit, he established a game preserve and eradicated natural predators. Land claim holders, mining prospectors, and other opponents tried to get his best efforts blocked, but the Grand Canyon was eventually established as the 17th U.S. National Park by Woodrow Wilson in 1919.

It doesn't get any easier for conservationists; recent concerns include uranium leaching into the water supply should mining recommence in the area, which has been suspended since 2009. The case rumbles on through the courts.