Saguaro National Park is a national park in the United States located in southeastern Arizona. The park covers 92,000 acres (37,000 hectares) and includes two separate areas: the Tucson Mountain District (TMD), which is about 10 miles (16 kilometers) west of Tucson, and the Rincon Mountain District (RMD), which is about 10 miles (16 kilometers) east of the city. Both areas protect Sonoran Desert landscapes, plants, and animals, including the large saguaro cactus.
The rocks on the surface of the Tucson Mountain District are very different from the rocks on the surface of the Rincon Mountain District. Over 30 million years ago, movements in the Earth’s crust moved rocks from beneath the Tucson Mountains to form the Rincon Mountains. These mountains are now higher and wetter than the Tucson Mountains. The Rincon Mountains, part of the Madrean Sky Islands between the southern Rocky Mountains and the Sierra Madre Oriental in Mexico, have many plants and animals that are not found in the Tucson Mountain District.
Before the park was created, people who lived in or visited the area included the Hohokam, Sobaipuri, Tohono O'odham, Apaches, Spanish explorers, missionaries, miners, homesteaders, and ranchers. In 1933, President Herbert Hoover used the Antiquities Act to create the original park, called Saguaro National Monument, in the Rincon Mountains. In 1961, President John F. Kennedy added the Tucson Mountain District to the monument and renamed the original area the Rincon Mountain District. In 1994, the United States Congress combined the Tucson Mountain District and the Rincon Mountain District to form the national park.
Popular activities in the park include hiking on 165 miles (266 kilometers) of trails and sightseeing along paved roads near the two visitor centers. Both districts allow bicycling and horseback riding on selected roads and trails. The Rincon Mountain District offers limited wilderness camping, but there is no overnight camping in the Tucson Mountain District.
Names
The park is named after the saguaro (Carnegiea gigantea), a large cactus that grows naturally only in the Sonoran Desert and is not found in other places. The word "Rincón," used in names like Rincon Mountains, Rincon Creek, and Rincon Valley, comes from Spanish and means "corner," describing the shape of the mountain range and its area. The name Tucson comes from Papago-Piman words "cuk ṣon [ˡtʃukʂɔn]," which mean "dark spring" or "brown spring." The words "Tank" or "Tanque" describe a small man-made pool behind a dam that collects water runoff in a natural depression. The term "Madrean" comes from the word "Madre" in Sierra Madre, which means "Mother Mountains."
Geography
The park is made up of two separate areas: the Tucson Mountain District (TMD) to the west of Tucson, Arizona, and the Rincon Mountain District (RMD) to the east. Each area is about 10 miles (16 km) from the center of the city. In 2016, the total area of both districts combined was 91,716 acres (37,116 ha). The Tucson Mountain District covers about 25,000 acres (10,000 ha), while the larger Rincon Mountain District covers the remaining 67,000 acres (27,000 ha). Approximately 71,000 acres (29,000 ha) of the park, including parts of both districts, is designated as wilderness.
Interstate 10, the main highway near the park, passes through Tucson. Tucson Mountain Park is located on the south side of the Tucson Mountain District, and the Avra Valley is to the west of the district. The Rincon Mountain Wilderness, a protected area of about 37,000 acres (15,000 ha) in the Coronado National Forest, is next to the Rincon Mountain District on the east and southeast. The Rincon Valley is directly south of the western part of the Rincon Mountain District.
Both districts protect parts of the Sonoran Desert, including the Tucson Mountains in the west and the Rincon Mountains in the east. Elevation in the Tucson Mountain District ranges from 2,180 to 4,687 feet (664 to 1,429 m), with Wasson Peak as the highest point. Elevation in the Rincon Mountain District ranges from 2,670 to 8,666 feet (814 to 2,641 m), with Mica Mountain as the highest point.
Saguaro National Park is located within the watershed of the north-flowing Santa Cruz River, which is usually dry. Rincon Creek, found in the southern part of the Rincon Mountain District, flows for part of the year and has the largest riparian zone in the park. Rincon Creek is a tributary of Pantano Wash, which crosses Tucson from southeast to northwest to meet Tanque Verde Wash. These two washes form the Rillito River, another dry wash that flows east-west and is a tributary of the Santa Cruz River. Washes in both districts are typically dry but can sometimes experience flash floods. Smaller riparian zones are found near springs and tinajas in the Rincon Mountain District. The largest spring is located at Manning Camp, high in the Rincon Mountains.
Climate
Saguaro National Park has a Hot semi-arid climate (BSh) according to the Köppen climate classification system. The United States Department of Agriculture reports that the Plant Hardiness zone at Red Hills Visitor Center, located at 2,553 feet (778 m), is 9b, with an average annual extreme minimum temperature of 25.8 °F (−3.4 °C). At Rincon Mountain Visitor Center, located at 3,091 feet (942 m), the zone is 9a, with an average annual extreme minimum temperature of 23.4 °F (−4.8 °C).
Short, intense summer rains often bring lightning, dust storms, and flash floods. Some areas at the highest elevations in the Rincons receive snow in winter. When this snow melts, it contributes to the limited water supply at lower elevations later in the year.
Research on climate change in the park shows that the average temperature each year increased by about 4 degrees Fahrenheit (2 degrees Celsius) from 1900 to 2010. Climate data below is from 2019.
Geology
Saguaro National Park's oldest rocks, called the Pinal Schist, are about 1.7 billion years old. These rocks are older than the Basin and Range Province, which includes the park. The schist can be seen in the Rincon Mountain District near a dry wash off Cactus Forest Loop Drive. Other very old rocks, 1.4-billion-year-old altered granites, make up much of Tanque Verde Ridge in the Rincon Mountain District.
About 600 million years ago, shallow seas covered the area around present-day Tucson. Over time, layers of sedimentary rocks—such as limestone, sandstone, and shale—formed. Limestone, found in several places in the park, was mined in the late 1800s to make mortar. The land that would later become the park had six lime kilns: two in the Tucson Mountain District and four in the Rincon Mountain District. Today, visitors can see three of these kilns—two along the Cactus Forest Trail and one along the Ruiz Trail.
Around 80 million years ago, movements of tectonic plates caused mountain-building activity called the Laramide orogeny, which lasted until about 50 million years ago in western North America. Volcanic eruptions formed the Tucson Mountains about 70 million years ago. The top of the volcano collapsed, creating a caldera 12 miles (19 km) wide. Over time, the caldera filled with debris flows, a granitic pluton, and lava flows, some as recent as 30 to 15 million years ago. Volcanic rocks in and near the Tucson Mountain District are remnants of these events. Examples include large breccia at Grants Pass and a granitic remnant of the magma chamber visible from the Sus Picnic Area. Not all molten granite reached the surface; some cooled and crystallized deep underground.
The Tucson Basin and nearby mountains—including the Tucson Mountains to the west, the Santa Catalinas to the north, and the Rincons to the east—are part of the Basin and Range Province, which stretches from northern Mexico to southern Oregon. This province formed when plate movements stretched and thinned Earth's crust in western North America, causing it to pull apart along faults. The Catalina Fault, a low-angle detachment fault, began forming about 30 million years ago, 6 to 8 miles (10 to 13 km) below the surface of the Tucson Mountains. Rocks below the fault were displaced 16 to 22 miles (26 to 35 km) east-northeast and later uplifted, domed, and eroded to form the Santa Catalina and Rincon mountains seen today. Although volcanic rocks on the surface of the Tucson Mountain District are not found in the Rincon Mountain District, crystallized granite (Catalina gneiss) from beneath the Tucson Mountains was exposed on the Rincon Mountain District's surface. This banded gneiss is the most common rock type in the Rincon Mountains and can be seen at sites like Javelina Rocks along the Cactus Forest Loop Drive.
History
The earliest people known to live in the area that later became Saguaro National Park were the Hohokam. They lived in villages from around AD 200 to 1450. Artifacts found in the park include petroglyphs and broken pottery. The Hohokam hunted deer and other animals, gathered cholla buds, prickly pears, palo verde pods, and saguaro fruit, and grew corn, beans, and squash. Later groups, such as the Sobaipuri of the Tucson Basin and the Tohono O'odham to the west, may have been descendants of the Hohokam, but there is not enough proof to be certain.
Spanish explorers first entered Arizona in 1539–40. Non-native people did not settle near the park until 1692, when the San Xavier Mission was built along the Santa Cruz River, which flows through Tucson. In 1775, the Spanish created Presidio San Agustín del Tucsón, a military fort in what was then part of New Spain, to protect against Apache raids.
The land that became Saguaro National Park remained mostly undeveloped until the mid-1800s, after Arizona joined the United States. After the Homestead Act of 1862, the arrival of the railroad in 1880, and the end of the Apache Wars in 1886, homesteaders and ranchers settled in the Tucson and Rincon Mountains. Miners also searched for silver, copper, and other valuable minerals. Mining in the park continued until 1942, while ranching on private land within the park lasted until the mid-1970s.
The Loma Verde Mine, now visible in the Rincon Mountain District, produced copper and gold from 1897 to 1907. In the Tucson Mountain District, mining of igneous rock at 149 sites sometimes yielded valuable ores in the late 1800s and early 1900s. The most successful mine, the Copper King Mine (later called the Mile Wide Mine), produced 34,000 tons of copper, gold, lead, zinc, and molybdenum ores mainly during the war years of 1917, 1918, and 1941. It closed permanently in 1942 when it became unprofitable.
Ranchers raised thousands of cattle on public land that later became part of the park. Homesteaders farmed and raised livestock near the Rincon Mountains, filing applications from the 1890s through 1930. The remains of the Freeman Homestead, established in 1929, are along a nature trail in the Rincon Mountain District. It is listed on the Arizona State Register of Historic Places. Manning Cabin, built in 1905 as a summer retreat for Levi Manning, a wealthy businessman and former mayor of Tucson, is part of Manning Camp near Mica Mountain. Restored after falling into disrepair, it was added to the National Register of Historic Places in 1975. The park includes more than 450 archaeological sites and over 60 historic structures.
In 1920, members of the Natural History Society of the University of Arizona wanted to create a protected area for saguaro cacti, which were familiar to fans of silent-movie Westerns. In 1928, Homer L. Shantz, a plant scientist and university president, supported the effort, but funding and management issues delayed the park’s creation. In 1933, Frank Harris Hitchcock, publisher of the Tucson Citizen and former U.S. Postmaster General, convinced President Herbert Hoover to establish Saguaro National Monument using his power under the Antiquities Act of 1906. Later that year, President Franklin D. Roosevelt transferred the monument’s management to the National Park Service. Between 1936 and 1939, the Civilian Conservation Corps (CCC) built the monument’s Cactus Forest Loop Drive and related infrastructure. The monument’s visitor center opened in the 1950s.
In 1961, President John F. Kennedy, encouraged by Stewart Udall, then Secretary of the Interior, added 16,000 acres of cactus land in the Tucson Mountains to the monument. This area, called the Tucson Mountain District, was carved from Tucson Mountain Park, managed by Pima County. In the 1920s, the Tucson Game Protective Association persuaded the Department of the Interior to set aside about 30,000 acres in the Tucson Mountains as a park and game refuge. Land leased by the county became the Tucson Mountain Recreation Area in 1932. Between 1933 and 1941, CCC workers built structures at eight picnic areas in the county-park portion of the set-aside, five of which later became part of the Tucson Mountain District. Their other projects included road and trail building, landscaping, erosion control, and improving water supplies for wildlife. Kennedy’s 1961 proclamation created the Tucson Mountain District from the northern part of the county park and renamed the original monument lands east of Tucson the Rincon Mountain District. Expansions in 1976 and 1994 increased the Tucson Mountain District’s area to 24,818 acres. In 1994, Congress elevated the combined Tucson Mountain and Rincon Mountain Districts to National Park status. The Consolidated Appropriations Act, 2021, added 1,232 acres to the park.
Biology
According to the A. W. Kuchler U.S. Potential Natural Vegetation Types, Saguaro National Park includes four vegetation classifications. These are: a Parkinsonia / Cactus (43) vegetation type with a Deserts and xeric shrublands (8) vegetation form; a Creosote bush scrub / Ragweed (42) vegetation type with a Deserts and xeric shrublands (8) vegetation form; a Bouteloua / Pleuraphis mutica Steppe (58) vegetation type with a Desert Steppe (14) vegetation form; and an Oak / Juniper Woodland (31) vegetation type with a Great Basin montane forests / Southwest Forest (4) vegetation form.
Plant communities in the park change with elevation. In the Tucson Mountain District, two main communities exist: desert scrub, such as fourwing saltbush and brittlebrush, at the lowest elevations, and desert grassland at slightly higher elevations. The Rincon Mountain District includes these communities and four more at higher elevations: oak woodland, pine–oak woodland, pine forest, and mixed conifer forest—Douglas-fir, Ponderosa pine, white fir, Gambel oak, and other trees, shrubs, and plants. Between 2011 and 2013, scientists and volunteers identified 389 species of vascular plants, 25 species of non-vascular plants, and 197 species of fungi in the park.
Saguaros grow in both districts of the park and grow very slowly. A saguaro’s first arm usually appears when the cactus is 50 to 70 years old, though this may occur closer to 100 years in areas with very little rain. Saguaros may live up to 200 years and are considered mature at about 125 years. A mature saguaro can grow up to 60 feet (18 meters) tall and weigh up to 4,800 pounds (2,200 kilograms) when fully hydrated. The park is estimated to have 1.8 million saguaros, along with 24 other cactus species. The most common are fishhook barrel, staghorn cholla, pinkflower hedgehog, Engelman’s prickly pear, teddybear cholla, and jumping cholla.
Invasive plants in the park include fountain grass, tamarisk, Malta starthistle, and others. The most serious threat to native plants is buffelgrass, a drought-tolerant plant from Africa and Asia. Introduced to the United States in the 1930s, it was planted near Tucson to provide cattle forage and control erosion. First found in the park in 1989, it has spread widely in both districts. Buffelgrass competes with native plants for resources and creates fire hazards. It is managed in some areas through hand-pulling and glyphosate-based herbicides during wet weather.
An inventory of medium and large mammals in the park between 1999 and 2008 confirmed the presence of 30 species. Twenty-one species were found in the Tucson Mountain District, and 29 species were found in the Rincon Mountain District. A partial list includes cougars, coyotes, bobcats, white-tailed deer, mule deer, javelinas, gray foxes, black-tailed jackrabbits, desert cottontails, ring-tailed cats, white-nosed coatis, ground squirrels, and packrats. One endangered species, the lesser long-nosed bat, lives in the park part of the year and in Mexico the rest of the year.
The park’s varied habitats support a wide range of birds, including some that are rare elsewhere in the United States, such as the vermilion flycatcher and the whiskered screech owl. The park is home to 107 bird species, including great horned owls, cactus wrens, ravens, kestrels, turkey vultures, roadrunners, woodpeckers, hawks, quails, hummingbirds, and one threatened species, the Mexican spotted owl.
The park has 36 reptile species, including desert tortoises, diamondback rattlesnakes, coral snakes, Gila monsters, short-horned lizards, spiny lizards, and zebra-tailed lizards. Three amphibian species live in the park despite the dry climate: the canyon tree frog, the lowland leopard frog, and Couch’s spadefoot, which lives in burrows and emerges to breed during summer rains. Forest fires have damaged many of the leopard frog’s breeding pools, which fill with sediment. The Arizona Game and Fish Department lists the lowland leopard frog as a species of special concern.
Urban sprawl, air and water pollution, noise, light pollution, and human infrastructure limit habitats for the park’s animals. The most serious immediate threat to wildlife is roadkill. About 50,000 vertebrates die each year on the park’s roads from vehicle collisions. The Rincon Mountain District has few roads, but Picture Rocks Road, a major highway in the Tucson Mountain District, is highly dangerous to wildlife. A 2002 proposal to convert the road into a hiking trail failed due to public opposition.
The Rincons and nearby Santa Catalinas (but not the shorter Tucson Mountains) are part of about 40 mountain ranges known as the Madrean Sky Islands. These ranges act like stepping stones between the southern end of the Rocky Mountains, specifically the Mogollon Rim of the Colorado Plateau, in the United States and the Sierra Madre Occidental in Mexico. These landmasses are separated by valleys that make it difficult but not impossible for species to move between them. Ecologist Peter Warshall notes that the Madrean Sky Islands are unique because of their north–south orientation across eight degrees of latitude, varied geology and soil types, high relief, and their distance from the mass extinctions caused by recent Ice Age glaciers. These conditions support high biodiversity in the region.
Recreation
The park is open to hikers all day every day except Christmas. The Tucson Mountain District allows vehicle traffic from sunrise to sunset, and the Rincon Mountain District is open from 7 a.m. to sunset. Both districts have visitor centers. Over 165 miles (266 km) of hiking trails are available in the park. Risks on the trails may include extreme heat, dehydration, flash floods, cactus spines, snakes, cougars, bears, and Africanized bees. The Rincon Mountain District allows wilderness camping with a permit, but no overnight camping is allowed in the Tucson Mountain District.
The Tucson Mountain District has 12 miles (19 km) of paved roads and 8.5 miles (13.7 km) of unpaved roads, including the 5-mile (8 km) Bajada Loop Drive. Bicycling is permitted only on paved roads, Bajada Loop Drive, Golden Gate Road, and the Belmont multi-use trail. Horses and other livestock are allowed on some trails.
Hohokam petroglyphs carved into large stones are easily found in the Tucson Mountain District. The Signal Hill Trail, which starts at the Signal Hill Picnic Area along the Bajada Loop Drive, leads to an area with many examples of 800-year-old rock art.
Notable artificial structures in the Tucson Mountain District include ramadas, picnic tables, and restrooms built by the Civilian Conservation Corps between 1933 and 1941. These rustic buildings use quarried stone and other local materials to blend with their surroundings.
The Arizona-Sonora Desert Museum is located just south of the Tucson Mountain District along North Kinney Road in Tucson Mountain County Park. This nonprofit organization operates on 98 acres (40 ha) rented from Pima County. It combines features of a botanical garden, zoo, and natural history museum, showcasing plants and animals native to the region.
The Rincon Mountain District includes the 8.3-mile (13.4 km) Cactus Forest Loop Drive, which provides access to some trails. A section of the Arizona Trail, which spans 800 miles (1,300 km) from Arizona’s border with Mexico to its border with Utah, crosses the Rincon Mountain District from southwest to northeast. Congress designated the Arizona Trail as a National Scenic Trail in 2009.
Horseback riding is allowed on some trails. Livestock, defined by the National Park Service as horses, mules, or burros, must bring their own food and are not allowed to graze in the park. Bicycling is permitted on the Cactus Forest Loop Drive and two park trails.
Manning Camp Campground is the main location for firefighters, trail-maintenance crews, and scientists working in the Rincon Mountain District. Supplies are transported by pack mules kept in corrals at the site. Water from a nearby spring, the largest in the Rincons, is used for livestock.
On a 40-acre (16 ha) plot near the Rincon Mountain District along Broadway, the Desert Research Learning Center (DRLC) supports scientific and educational projects related to a network of Sonoran Desert parks, including Saguaro National Park. The DRLC grounds, which include desert plants, an artificial tinaja, and a rainwater collection system, are open to the public. The Sonoran Desert Inventory and Monitoring Network, of which the DRLC is a part, covers 10 national monuments or parks in Arizona and one in New Mexico.