The Sonoran Desert takes up over 100,000 square miles and covers parts of two states and two countries: the southern parts of Arizona and California in the United States and large parts of the states of Sonora, Baja California Norte and Baja California Sur in Mexico. You’ve probably read that the Sonoran Desert is one of the most wildly diverse deserts in the world, but it is also one of the most ecologically balanced deserts in the world.