What Arizona national park was formed over millions of years by the relentless efforts of the Colorado River?
Colorado Canyon Grand Canyon (Ariz.) Grand Canyon, AZ North Rim of the Grand Canyon Grand Canyon The Great Canyon Grand canyon Canon of Colorado The Grand Canyon North Rim Great Colorado Canyon Grand canynon Grand Canyon of the Colorado Grand Canyon Park Act of 1919 Lipan Point Grand Canyon of the Colorado River South Rim Ongtupqa Great Canyon Grand Canyon, Arizona