Southwestern United States

The Southwestern United States is a vast geographic and cultural region.

It is often called the American Southwest. The region includes the states of Arizona and New Mexico. It also contains parts of California, Colorado, Nevada, Oklahoma, Texas, and Utah. Because there is no official boundary, definitions vary. Some define it by longitude and latitude. Others focus on the core states of Arizona and New Mexico.

The region is known for its distinct landscapes and diverse cultural heritage.

The geography is defined by four primary features. These are the Mojave, Sonoran, and Chihuahuan Deserts, and the Colorado Plateau. The deserts dominate the southern and western areas. The Colorado Plateau is a high desert region in the north.

Two major rivers shape the land. The Colorado River flows through the northern and western parts. The Rio Grande flows through the east from north to south. These water sources are vital to the arid environment.

The Chihuahuan Desert is a major part of the southeastern Southwest. It formed about 8,000 years ago. This desert is a "rain shadow" desert. This means the Sierra Madre Occidental and Sierra Madre Oriental mountains block rain from the ocean.

It is the second largest desert in the United States. Only one third of it is in the U.S., while the rest is in Mexico. It is the most biologically diverse desert in the Western Hemisphere. It contains more cactus species than any other desert in the world. Many mountain ranges, like the Organ and Sandia Mountains, rise from it. These mountains create "sky islands" with different plants and animals. They also provide water through spring runoff and summer monsoons.

The Sonoran Desert covers the southwestern portion of the region. It sits on the southeastern border of California and western southern Arizona.

This desert is famous for the saguaro cactus. This plant is unique to the Sonoran. The desert also has many other cacti, such as the prickly pear and cholla. It has the most diverse plant life of any desert in the world. The Sonoran is also the most populated part of the Southwest. Six of the region's top ten population centers are here. These include Phoenix and Tucson in Arizona.

The Mojave Desert is in the far northwest of the region. It covers parts of Nevada, Utah, and Arizona.

It is the smallest, driest, and hottest desert in the United States. It receives less than 6 inches of rain every year. The elevation ranges from 3,000 to 6,000 feet. The most famous plant here is the Joshua tree. These trees can grow 40 feet tall. They may live for almost 1,000 years. The Mojave is bordered by the Sonoran Desert and the Colorado Plateau.

The Colorado Plateau is a massive feature in the north. It consists mostly of high desert. It is famous for its plateaus, mesas, and deep canyons.

The Grand Canyon is the most dramatic example of this landscape. The Plateau is very old. It came into existence at least 500 million years ago. It is divided into six sections. Three of these sections fall within the Southwest. These include the Navajo section, the Grand Canyon section, and the Datil section. The Datil section contains valleys and volcanic formations.

Human history in the Southwest began with the Clovis culture around 9000 BC.

Later, three major Pre-Columbian cultures emerged. The Ancestral Pueblo people began settling around 1500 BC. They moved from pithouses to larger pueblos. The Mogollon culture developed around 300 BC in the east. They eventually built cliff-dwellings. The Hohokam culture developed around AD 1. They were the most populous of the three by AD 1300. They built extensive irrigation canals to water their crops. By the end of the 15th century, these cultures declined for unknown reasons.

The modern history of the region changed in the mid-1800s. Much of the land was once part of New Spain and Mexico. The United States acquired the territory through two main events. First, the Treaty of Guadalupe Hidalgo was signed in 1848. Later, the Gadsden Purchase occurred in 1854.

This history created a unique blend of cultures. Today, the region features Southwestern cuisine, like Tex-Mex and New Mexican styles.

It also has unique architecture, such as Pueblo Revival and Spanish Colonial styles. This reflects the heritage of Native Americans, Hispano, Mexican American, and cowboy cultures.