Canyon Diablo is an 81-mile gorge in northern Arizona carved into the Colorado Plateau beginning roughly 2 to 3 million years ago, with channels that sometimes feed the Little Colorado River. Its geology includes Kaibab Limestone and parts of the Moenkopi Formation, and its basin covers about 1,180 square miles. People lived around the canyon long before modern transportation, including Sinagua communities and earlier hunter-gatherers. In the 19th and 20th centuries it became both a barrier and a corridor, shaping railroad and highway crossings that encouraged nearby settlement. The canyon is also closely tied to Meteor Crater and to the Canyon Diablo meteorite, later used in research on Earth’s age.