The desert covering parts of Arizona, California, Sonora, and Baja California is the Sonoran Desert.
This hot desert stretches around the northern end of the Gulf of California. Its range includes southwestern Arizona and southeastern California in the United States, plus large parts of Mexico’s Sonora and Baja California regions. Some descriptions also include Baja California Sur, reflecting the desert’s broader biogeographic reach.
The Sonoran stands out from neighboring deserts because it receives rainfall in two seasons in many areas: winter storms and summer monsoon rains. That pattern supports more plant life than the colder Great Basin Desert and helps distinguish it from the Mojave, whose summer is typically much drier. The iconic saguaro cactus and organ-pipe cactus are signature Sonoran species.
The nearby Colorado Desert is commonly treated as a subregion of the Sonoran Desert, while the Baja California Desert is a separate neighboring ecoregion. Those overlapping labels can make maps look inconsistent, but the four territories named in the question are the classic geographic footprint of the Sonoran Desert.