A desert is defined primarily by low annual precipitation, receiving less than 10 inches (25 centimeters) of moisture per year, and not necessarily by scorching heat. North America contains four vast, distinct desert systems covering large portions of the continent’s arid interior. While the borders of these ecosystems can sometimes blur, there is a clear consensus on which one holds the title of largest. This distinction is based on the sheer expanse of the region and its unique geological and ecological features.
Identifying the Largest North American Desert
The biggest desert in North America is the Great Basin Desert, a massive expanse dominating the continent’s arid landscape. Its estimated area is approximately 190,000 to 200,000 square miles (492,000 to 518,000 square kilometers), making it substantially larger than the other North American deserts. This region is located between the Sierra Nevada and Cascade mountain ranges to the west and the Wasatch Mountains to the east.
The desert stretches across the western United States, covering nearly all of Nevada and the western half of Utah. Smaller sections also extend into eastern California, southern Idaho, and southeastern Oregon. The Great Basin’s size and isolation contribute to its distinct ecological profile.
Defining Characteristics of the Great Basin
Unlike the hot, arid deserts typically imagined, the Great Basin is classified as a “cold desert,” characterized by extremes in temperature. While summers are hot and dry, winters are often frigid and snowy, with much of the limited precipitation falling as snow. This high-desert ecosystem features elevations typically ranging from 4,000 to 6,000 feet (1,200 to 1,800 meters) in its valleys, leading to sharp temperature drops between day and night.
The desert’s existence is a direct result of the rain shadow effect created by the Sierra Nevada and Cascade ranges. As moisture-laden air from the Pacific Ocean is forced up and over these mountains, it cools and releases its water on the western slopes. By the time the air descends on the eastern side, it is extremely dry, creating the parched conditions of the Great Basin.
The vegetation is dominated by low, drought-tolerant shrubs, lacking the large cacti or succulents found in southern deserts. The indicator plant for this cold desert is the big sagebrush (Artemisia tridentata), which covers vast expanses in dense shrubland known as sagebrush steppe. Other common plants include various species of saltbush (Atriplex), which thrive in the high-saline soils of ancient lakebeds.
The fauna is well-adapted to the high-elevation, cold conditions, including animals like the pinyon jay. The pinyon jay relies on the seeds of the pinyon pine and juniper trees found on the mountain slopes. The internal drainage system is a unique feature, meaning precipitation drains into closed basins and ephemeral salt lakes, never reaching an ocean.
Contrasting the Other Major North American Deserts
The three other major North American deserts—the Mojave, Sonoran, and Chihuahuan—are categorized as “hot deserts” and occupy lower elevations than the Great Basin. The Chihuahuan Desert extends deeply into Mexico and covers approximately 193,783 square miles (501,896 square kilometers). It is sometimes cited as the largest, but it is specifically the largest hot desert on the continent. This desert is known for its high species richness, including cacti and succulents like agave and prickly pear.
The Sonoran Desert, covering parts of Arizona, California, and Mexico, is the hottest of the four, but also the most biologically diverse due to its bimodal rainfall pattern. It receives both winter rains and summer monsoons, allowing for the growth of its signature columnar cactus, the saguaro (Carnegiea gigantea). This increased moisture and warmer climate distinguish it sharply from the cold, shrub-dominated terrain of the Great Basin.
The Mojave Desert, located primarily in California and Nevada, is considered the smallest and driest of the four. It is the location of Death Valley, which holds the record for the lowest elevation and highest recorded air temperature in North America. Its landscape is defined by the iconic Joshua tree (Yucca brevifolia), which thrives at lower elevations. These hot deserts share a common distinction from the Great Basin: their lower latitude and elevation result in warmer, less snowy conditions supporting different indicator species.