Looking down into the canyon from its rim, one sees massive rock formations stretching into the distance that vary in color according to the season and hour of day. In 1908 President Theodore Roosevelt set aside a portion of the canyon as a national monument.

In 1919 it was expanded to cover more than 1000 sq. miles and was designated as the Grand Canyon National Park. An additional part of the canyon was included in newly established Grand Canyon National Monument in 1932. In 1975 the national park was enlarged to include the national monument and other areas. The entire canyon is now within the park, which is 1904 sq. miles in size.

Numerous national monuments, all of them administered by the National Park Service, lie within the borders of Arizona. Most of the monuments preserve the remains of Arizona's prehistoric peoples, who lived communally in houses built in the faces of vertical cliffs high above the canyon floors and provided for their needs by cultivating the fertile valleys at the bottom with the help of often skillfully contrived irrigation systems.

Montezuma Castle National Monument preserves a 5-story, 20-room cliff dwelling south of Flagstaff. Navajo National Monument offers an array of multiple-roomed cliff-house ruins dating from before 1300. Other cliff-dweller sites are preserved at Walnut Canyon National Monument, Tonto National Monument, and Canyon de Chelly National Monument.

Ruins that may antedate the cliff houses are found at Casa Grande Ruins National Monument, Tuzigoot National Monument, and Wupatki National Monument. Hohokam Pima National Monument preserves archaeological remains of the Hohokam culture.

European exploration and settlement of the Arizona region is commemorated in several national parks and monuments, including those recognizing the conflicts that developed between the Native Americans and Europeans. Coronado National Memorial details the first major European exploration of the Southwest.

Fort Bowie National Historic Site tells the story of the bitter conflict between the Chiricahua Apaches and the United States military. It was the site where a large force of Chiricahua Apaches under Mangus Colorados and Cochise fought the California Volunteers, and where Chief Geronimo was captured in 1886 after ten years of sporadic raids.

Arizona Indian Lands

The influence of traders on the lives of Native Americans can be seen at the still-active Hubbell Trading Post National Historic Site. Tumacacori National Historical Park includes a historic Spanish Catholic mission near the site first visited by Jesuit missionary Eusebio Francisco Kino in 1691. Pipe Spring National Monument contains a fort built by early Mormon pioneers.

Arizona's rich natural environment is preserved in several parks. Chiricahua National Monument and Sunset Crater Volcano National Monument are examples of violent volcanic eruptions that shaped the countryside millions of years ago. Some 1000 times more powerful than the 1980 eruption of Mount Saint Helens, the Turkey Creek Caldera eruption in Chiricahua eventually laid down 600 m (2000 ft) of ash and pumice. This mixture fused into a rock that eventually eroded into the spires and unusual rock formations seen today.

Giant saguaro cacti, unique to the Sonoran Desert, sometimes reach a height of 50 feet in the cactus forest of Saguaro National Park. Organ Pipe Cactus National Monument preserves a section of the Sonoran Desert. Trees that have petrified, or changed to multicolored stone, are features of the Petrified Forest National Park, as are Native American ruins and petroglyphs, and a portion of the colorful Painted Desert.

The national park service also oversees two popular national recreation areas in the Arizona, at Glen Canyon and Lake Mead.