Grand Canyon in northern Arizona is a vast chasm carved by the Colorado River through the Colorado Plateau, stretching 277 miles, reaching up to 18 miles wide, and dropping more than a mile deep. Its cliffs reveal nearly two billion years of Earth’s history, making it one of the world’s most important geological landscapes. The canyon formed through a complex process, with different segments developing at different times, while much of its present depth was cut in the last 5 to 6 million years after uplift and changes in the river accelerated erosion. It is also a long-inhabited sacred landscape for Native peoples and a major preserved American landmark.