The essential guide to Arizona's national parks

Grand Canyon National Park is one of Arizona's most famous sights. Photo / 123RF

Home to one of the world's natural wonders as well as one of its largest cactus species and an astonishing petrified forest, Arizona's national parks will leave visitors' jaws hanging

As the USA's National Park Service celebrates its centenary, we're profiling the wilderness areas it manages.

Today: The national parks of Arizona . . .

Grand Canyon National Park

"It became an obsession. . . . I was determined to put it all to music."
- Ferde Grofé, composer of 'The Grand Canyon Suite'

The Colorado River gorge is notable for its depth (1.6km, on average), as well as its variegated colours. It's regarded as one of the seven wonders of the natural world and is a UNESCO World Heritage site. The organisation describes it on its website as "the most spectacular gorge in the world".

Its dramatic beauty draws visitors from around the world. In a 2005 tourism study, 17 percent of Grand Canyon visitors needed a passport to get to it.

Vistas here have moods. Hues change by time of day and season, and canyon views vary by the perspective from all four directions (rims).

The South Rim (open all year) is the most accessible and offers classic views most associated with the canyon. Wheelchair-accessible bus tours are available. (Reservations are a must.) The Bright Angel Trail is smooth and easy to navigate. The North Rim is smaller, less visited and typically is cooler.

Sunset at Grand Canyon National Park. Photo / 123RF

Those who hike to the bottom pass, geologically speaking, through a third of the earth's existence. At the base of this naturally carved spectacle is the Colorado River, which draws water from seven states and travels 2334 kilometres from its Rocky Mountains source to the Gulf of California.

Size: 1,201,647 acres

Founded: National monument, 1908; national park, 1919

Attendance: 5,520,736 (2015)

Petrified Forest National Park

"A kaleidoscope fashioned by God's hand."
- John Muir, naturalist

Blue mesa in Petrified Forest National Park. Photo / 123RF

A faded remnant of the historic Route 66 unpaved roadbed here is a mere newcomer within the surrounding context of ancient fossils going back more than 200 million years, Pueblo structures and petroglyphs, which are visible on Newspaper Rock.

The park is best known for having the world's largest and most colorful collection of petrified wood. The brilliant hues — blue, purple, red, yellow, black and brown — come from the elements that replaced the organic materials. The petrified wood, which weighs about 2563 to 3204 kilograms per cubic metre, was deposited in the park's various forests more than 200 million years ago.

The broken trunk of a petrified tree in Arizona's Petrified Forest National Park. Photo / 123RF

Although the terrain is challenging, the main park road runs 45km, with spurs and viewpoints along the way. Bicycles are permitted in paved and public areas. Among the sites of interest is the 1920s-era Painted Desert Inn National Historic Landmark, two miles from the north entrance. The former Route 66 accommodation, now restored as a museum, overlooks the Painted Desert, the multicolored badlands that stretch nearly to the Grand Canyon.

Size: 218,533 acres

Founded: National monument, 1906; national park, 1962

Attendance: 793,225 (2015)

Saguaro National Park

"It ranks with the great redwoods."
- Homer L. Shantz, botanist and president of the University of Arizona in the early 1900s

Saguaro cactus plants take 200 years to reach their full height of more than 13 metres. Photo / 123RF

In addition to the famed giant cactuses, much of the park is a vast, federally designated wilderness that includes a desert ecosystem, mountains and Native American cultural traditions.

Among its natural wonders is this: It can take the saguaro 10 years to reach a height of one inch (2.54cm). After a century, it can hit 4.6 metres and display the beginning of its first arm. After 200 years, a saguaro reaches its full average height of 13.7m. Fully hydrated examples can weigh up to 2177kg.

The park has two separate districts: Tucson Mountain (west) and Rincon Mountain (east), each with its own entry centre. The west side has the largest stands of saguaro and the east has sky islands (mountains rising from the desert) with diverse animal life.

Highlights may be viewed via accessible trails, picnic areas and interpretive centres.

Size: 91,442 acres

Founded: National monument, 1933; national park, 1994

Attendance: 678,261 (2015)