The Grand Canyon cuts through northwestern Arizona.Grand Canyon National Park, a unit of the National Park System in northwestern Arizona. It encompasses all of the Grand Canyon, an enormous gorge carved into a high plateau by the Colorado River, beginning at least 5,000,000 years ago. The canyon is roughly 200 miles (320 km) long and is as much as one mile (1,600 m) deep and 18 miles (29 km) wide. The park has an area of 1,904 square miles (4,931 km 2 ).
The rock strata (layers) of the Grand Canyon show about 2 billion years of the earth's geologic history. Towering, carved formations of limestone, sandstone, and shale rise from the canyon floor. The strata vary in color and display different hues throughout the day, as the sunlight changes.
Lookout points and park facilities, including campgrounds and lodging, are located on the North Rim and South Rim of the canyon. The canyon's highest accessible spot, Point Imperial, is on the North Rim—8,803 feet (2,683 m) above sea level. The North Rim's Cape Royal and Bright Angel Points also offer superb views of the canyon. The South Rim, from 1,000 to 2,000 feet (300 to 600 m) lower in elevation than the North Rim, is the main tourist area. The park headquarters, a visitor center, museums, and picnic areas are here. The North Rim is closed in the winter because of heavy snow; the South Rim is open year-round. Millions of people from many nations visit the Grand Canyon each year.
Trips into the canyon are made in several ways. The most popular trails are Bright Angel, which descends from the South Rim, and Kaibab Trail, which links the North and South Rims. They can be travelled either on foot or by mule. Raft and boat trips down the Colorado River are also exciting ways to see the canyon.
Scouts sent out by Francisco Vásquez de Coronado in 1540 were the first Europeans to sight the Grand Canyon. The first scientific exploration of the canyon was made by Major John Wesley Powell, a geologist who led an expedition down the Colorado River in 1869. The canyon was made a national monument in 1908; the national park was established in 1919 and expanded in 1974. The National Park Service of the U.S. Department of the Interior administers the park.
