Established as a National Monument in 1933 and designated as a National Park in 1994, the Saguaro National Park, covering an area of around 372 sq km, is located in the southeastern part of Arizona, USA and consists of two separate units, namely the Tucson Mountain District in the west and the Rincon Mountain District in the east, separated by the city of Tucson. The Park preserves the landscape, flora and fauna of the Sonoran Desert area and was named after the giant Saguaro cactus, the universal symbol of the western USA and native to only the Sonoran Desert and the northwestern part of Mexico and not in any other place on the planet.

Both the Tucson and the Rincon Mountain districts, containing parts of the Sonoran Desert, are surrounded by the Tucson Mountains in the west and the Rincon Mountains in the east. The elevations in the Rincon Mountains, ranging from 2,670 to 8,666 feet (814 to 2,641 m) are taller than that of the Tucson Mountains, ranging from 2,180 to 4,687 feet (664 to 1,429 m). The Mica Mountain, located in the Rincon Mountain District area and rising to an elevation of 8668 feet (2642 m), is the highest point in the Rincon Mountains, as well as the Saguaro National Park.

The Saguaro National Park has a rich geological history. The dark grey metamorphic rocks, known as Pinal Schist, which are the oldest rocks found in the park, are estimated to be approximately 1.7 billion years old. Scholars maintain that around 70 million years ago, explosive volcanic eruptions formed the Tucson Mountains and the roof of the volcano at their centre collapsed to form a caldera, a large cauldron-like hollow, formed after the volcanic eruption, which was eventually filled by the lava flows and debris, approximately 30 to 15 million years ago.

The exposed volcanic rocks found in and around the Tucson Mountain District are remnants of those geological events. However, although the volcanic rocks seen on the surface of the Tucson Mountain District are not found in the Rincon Mountain District, the crystallized granite beneath the Tucson Mountains was eventually exposed on the Rincon Mountain District's surface, visible at some sites such as Javelina Rocks, along the Cactus Forest Loop.

It is believed that from 200 to 1450 AD the present Park area was inhabited by the Hohokam people, and after that, other indigenous people, namely the Sobaipuri, Apaches and the Tohono O’odham also lived in the area. Subsequently, although the Spanish explorers first entered Arizona in 1539-1540, non-native settlement of the region near the Park did not occur until 1692 with the founding of San Xavier Mission along the Santa Cruz River.

Gradually, the ranchers established themselves in the Tucson and Rincon Mountains, while the miners took care of the silver, copper, lead and other valuable ores and minerals. However, the huge area covering the Saguaro National Park remained relatively free of development until Arizona became part of the United States on 14 February 1912. In 1920, some members of the University of Arizona’s Natural History Society decided to protect the area for the conservation of the giant Saguaro cactus, a huge plant which by that time became familiar to the lovers of the western silent-movies, as well as to protect the biodiversity of the Sonoran Desert. However, on 1 March 1933, the then US President Herbert Hoover proclaimed the area as the Saguaro National Monument and after that, President John F Kennedy added about 6500 sq km of cactus land to the Saguaro National Monument in 1961, creating the Tucson Mountain District in the west and renaming the original land covering the National Monument as the Rincon Mountain District in the east. Finally, the US Congress combined those two separate districts and established the Saguaro National Park on 14 October 1994.

The diverse habitats of the Saguaro National Park support a variety of plants, which vary with elevation. The Tucson Mountain District features desert scrubs, like flowering saltbush and brittlebush at lower elevations and desert grassland at higher elevations, while apart from those two, the Rincon Mountain District features oak woodland, pine-oak woodland, Ponderosa pine, Gambel oak and the like at higher elevations. However, both the districts in the Park feature the native giant saguaro cactus, estimated about 1.8 million in number, which include some 24 species of the cactus, like Engelmann’s prickly pear, pink flower hedgehog, jumping cholla, teddybear cholla, fishhook barrel and others. Saguaros can grow to be over 40 feet (12 m) tall and have a relatively long lifespan, often exceeding 150 years, but they grow at an exceptionally slow rate. The first arm of a saguaro typically appears when the cactus is between 50 and 70 years old, which are developed to increase the plant's reproductive capacity, leading to more flowers and fruit.

Saguaros bear white blossoms, the Arizona state flower, and sweet red fleshed edible crimson fruits, which are turned into syrup by the native people, The holes in their trunks and branches, created by the Gila woodpeckers and gilded flickers serve as nesting places for wrens, owls and other small birds, while their ribs are used as building materials in the wood-poor deserts. Saguaros can absorb and store a considerable amount of rainwater, making them visibly expanding in the process, while slowly using the stored water as needed, which make them survive during the periods of drought.

Between 1999 and 2008, a study confirmed the presence of 30 species of mammals in the Park, out of which 21 were found in the Tucson Mountain District and 29 in the Rincon Mountain District, which include, among others, white-tailed deer, mute deer, coyotes, javelinas, black-tailed jackrabbits, grey foxes, desert cottontails, ground squirrels, ring-tailed cats and the endangered mammal, lesser long-nosed bat. The park's 36 reptile species include coral snakes, diamondback rattlesnakes, Gila monsters, desert tortoises, spiny lizards, short-horned lizards, while 3 amphibian species include Couch’s spadefoot, canyon tree frog and lowland leopard frog. The wide range of habitats in the park also supports a diverse population of birds like cactus wrens, woodpeckers, ravens, hummingbirds, hawks, kestrels, the highly threatened Mexican spotted owl, along with some others that are uncommon elsewhere in the States, such as the whiskered screech owl and the vermillion flycatcher.

Though the conditions in the blazing hot and dry Sonoran Desert may seem inhospitable, the Saguaro National Park is considered as a photographer's paradise, and has a lot to offer to the visitors, which include its uncommon giant plants amid a dramatic backdrop of the terracotta-tinted mountains and the endless blue sky. The Park encompasses numerous hiking trails that wind through the stunning desert scenery, equipped with resting benches and all within easy reach of the restaurants, shops and galleries of Tucson.