[5] The earliest known residents of the land in and around what later became Joshua Tree National Park were the people of the Pinto Culture, who lived and hunted here between 8000 and 4000 BCE.

[6] Their stone tools and spear points, discovered in the Pinto Basin in the 1930s, suggest that they hunted game and gathered seasonal plants, but little else is known about them.

[8] In 1772, a group of Spaniards led by Pedro Fages made the first European sightings of Joshua trees while pursuing native converts to Christianity who had run away from a mission in San Diego.

By 1823, the year Mexico achieved independence from Spain, a Mexican expedition from Los Angeles, in what was then Alta California, is thought to have explored as far east as the Eagle Mountains in what later became the park.

Three years later, Jedediah Smith led a group of American fur trappers and explorers along the nearby Mojave Trail, and others soon followed.

[21] The monument was redesignated as a national park on October 31, 1994, by the Desert Protection Act, which also added 234,000 acres (365.6 sq mi; 947.0 km2).

[22] In 2019, the park expanded by 4,518 acres (7.1 sq mi; 18.3 km2) under a provision included in the John D. Dingell, Jr. Conservation, Management, and Recreation Act.

[26] The higher and cooler Mojave Desert is the special habitat of Yucca brevifolia, the Joshua tree for which the park is named.

In addition to Joshua tree forests, the western part of the park includes some of the most interesting geologic displays found in California's deserts.

When the area regenerates, these non-native grasses form a thick layer of turf that makes getting a roothold harder for the pine and oak seedlings.

According to the United States Department of Agriculture, the plant hardiness zone at the Cottonwood Visitor Center at 3081 ft (939 m) elevation is 8b, with an average annual extreme minimum temperature of 19.8 °F (−6.8 °C).

Much later, from 250 to 75 million years ago, tectonic plate movements forced volcanic material toward the surface at this location and formed granites, including monzogranite common to the Wonderland of Rocks, parts of the Pinto, Eagle, and Coxcomb Mountains, and elsewhere.

[34] The rock formations of Joshua Tree National Park owe their shape partly to groundwater, which filtered through the roughly rectangular joints of the monzonite and eroded the corners and edges of blocks of stone, and to flash floods, which washed away covering ground and left piles of rounded boulders.

Shorter trails, such as the one-mile hike through Hidden Valley, offer a chance to view the beauty of the park without straying too far into the desert.

The rocks are all composed of quartz monzonite, a very rough type of granite, made even more so as no snow or ice polishes it as in places such as Yosemite.

As of March 14, 2018[update], seasonal closures include the Slatanic Area, Towers of Uncertainty, Patagonia Pile, and Jerry's Quarry.

Many migrating species spend only a short time feeding and resting at Joshua Tree, mainly in the winter, as the park lies along an inland stretch of the Pacific Flyway.

[48] Joshua Tree is a popular observing site in Southern California for amateur astronomy and stargazing,[49] along with nearby Anza-Borrego Desert State Park.

The park's elevation and dry desert air, along with the relatively stable atmosphere in the region, often make for excellent seeing conditions.

The park is well known for its naturally dark night skies, which are far away from and largely free of the light pollution typical in urban areas.

[52][53] In the easternmost regions of the park, visitors with optimal vision can expect to see the Andromeda (M31) and Triangulum (M33) galaxies with unaided eyes.

In addition to the many birds, such as Gambel's quail and the greater roadrunner, numerous lizards, snakes, chipmunks, and California ground squirrels are the animals most likely to be seen by daytime visitors to the area.

[47] Golden eagles, ravens, red-tailed hawks, burrowing owls and turkey vultures are among the diurnal raptors and predatory birds that can be seen in the park, as they hunt, sun themselves on rocks, or scan the grounds for carrion.

Reclusive, but nocturnally-active, mammalian species include the American badger, black-tailed jackrabbit, bobcat, coyote, desert bighorn sheep, gray fox, kangaroo rat, mountain lion, mule deer and ringtail.

[59] The desert tortoise, a threatened reptile species that inhabits the creosote (Larrea tridentata)-studded lowlands of the Mojave Desert, is well-adapted to arid conditions; instead of drinking water directly, most of the tortoise's water is obtained from consuming the creosote bush as well as prickly pear (Opuntia sp.)

[60] The creosote is not only a favorite food for the desert tortoise, but is also one of the primary plants eaten by the chuckwalla, a large, diurnal lizard species.

[61] The red-spotted toad (Bufo punctatus) is a true denizen of the desert, as it spends most of its life buried underground in a state of torpor, awaiting seasonal rains to emerge and breed en masse.

[61] The tarantula species Aphonopelma iodium, the green darner (Anax junius) and the giant desert scorpion (Hadrurus arizonensis) are three larger arthropods that can grow to be more than 4 inches (10 cm) long.

By comparison, winter is the time of greatest birdwatching opportunities in the park, with the region being a prime "rest-stop" for many migratory species on their annual flights to warmer locales.

Casey Schreiner (of the hiking blog Modern Hiker) and some of his followers aided the National Park Service in locating and identifying André's vandalism.