The Chihuahuan Desert is the largest desert in North America, covering over 500,000 square kilometers across the Southwestern United States and Northern Mexico. It is bounded by the Sierra Madre Occidental and Sierra Madre Oriental mountain ranges, which create a rain shadow that prevents moisture from the Pacific and Gulf of Mexico from reaching the interior. Unlike the Sonoran Desert, which has two rainy seasons, the Chihuahuan is a 'rain-shadow' desert that receives most of its moisture during the summer months. It is characterized by high-altitude plateaus and a vast diversity of cactus species. One of its most famous features is Big Bend National Park, where the Rio Grande carves deep canyons through the desert limestone. It is also home to the Mexican wolf and the pronghorn, the fastest land animal in North America.