The Grand Canyon in a moonlit night. Constellation Auriga with bright star Capella appears in the sky. The Grand Canyon in northern Arizona is the longest canyon on the Earth, a steep-sided gorge carved by the Colorado River steadily in about 17 million year time span. The canyon is 446 km long, ranges in width from about 6 to 29 km and attains a depth of more than 1.6 km or about a mile.