Grand Canyon National Park - Arizona

Established February 26, 1919

1,218,376 acres

The road to the Grand Canyon from the south crosses a gently rising plateau that gives no hint at what is about to unfold. You wonder if you have made a wrong turn. All at once an immense gorge a mile deep and up to 18 miles wide opens up. The scale so vast that even from the best vantage point only a fraction of the canyon's 277 miles can be seen.

Nearly five million people travel here each year; 90 percent first see the canyon from the South Rim with its dramatic views into the deep inner gorge of the Colorado River. So many feet have stepped cautiously to the edge of major overlooks that in places the rock has been polished smooth. But most of the park's 1,904 square miles are maintained as wilderness. You can avoid crowds by hiking the park's many trails or driving to the cool evergreen forests of the North Rim where people are fewer and viewing more leisurely.

Canyon views are not always clear, though you can see 100 miles on a good day. Increasingly, air pollution blurs vistas that had once been sharp and rich hued. Hazy days have become more common, with visibility dropping as low as 20 miles. Haze from forest fires and pollen has always been present, but the recent increase is traced to sources outside the park, like copper smelters and urban areas in Arizona, southern California, and even Mexico.

It's hard to look at the canyon and not be curious about geology. Some of the oldest exposed rock in the world, dating back 1.8 billion years,

lies at the bottom. Exactly how the river formed the canyon is still unclear, but geologists generally agree that most of the cutting occurred within the last five million years.