The Grand Canyon -- 277 miles long, and up to 18 miles wide reaches a depth of over a mile (6,093 feet) -- exposes nearly two billion years of Earth's geological history as the Colorado River and its tributaries cut their channels through layer after layer of rock while the Colorado Plateau was uplifted. The canyon is the result of erosion which exposes one of the most complete geologic columns on the planet and is often considered one of the Seven Natural Wonders of the World.
The more recent Kaibab limestone caprock, on the rims of the Grand Canyon, formed 270 million years ago. In contrast, the oldest rocks within the Inner Gorge at the bottom of Grand Canyon date to 1.84 billion years ago. Geologists currently estimate the age of Earth at 4.5 billion years.
The Cambrian seas of the Grand Canyon were home to several kinds of trilobite, whose closest living relative is the modern horsehoe crab. They left their fossil record in the mud of the Bright Angel Shale over 500 million years ago.
Grand Canyon National Park was officially designated as a national park in 1919, though the landmark had been well known to Americans for over thirty years prior. In 1903, President Theodore Roosevelt visited the site and said: "The Grand Canyon fills me with awe. It is beyond comparison—beyond description; absolutely unparalleled through-out the wide world... Let this great wonder of nature remain as it now is. Do nothing to mar its grandeur, sublimity and loveliness. You cannot improve on it. But what you can do is to keep it for your children, your children's children, and all who come after you, as the one great sight which every American should see."
The original photograph by Robert B. Decker for this Grand Canyon National Park poster was taken from the Kolb Studio, which was once the home and business of the Kolb brothers, pioneering photographers at Grand Canyon. The studio is located in the Village Historic District, at the Bright Angel Trailhead, where each year, thousands of hikers enter the Grand Canyon. They follow a route established by prehistoric people for two key reasons: water and access. Water emerges from springs at Indian Garden, and a fault creates a break in the cliffs, providing access.