The Atacama Desert is a plateau in South America, covering a 1,000-kilometre (600 mi) strip of land on the Pacific coast, west of the Andes mountains. It is the driest non-polar desert in the world. According to estimates the Atacama Desert proper occupies 105,000 square kilometres (41,000 sq mi), or 128,000 square kilometres (49,000 sq mi) if the barren lower slopes of the Andes are included. Most of the desert is composed of stony terrain, salt lakes (salares), sand, and felsic lava that flows towards the Andes.
The World Wide Fund for Nature defines the Atacama Desert ecoregion as extending from a few kilometers south of the Peru-Chile border to about 30° south latitude. The National Geographic Society considers the coastal area of southern Peru to be part of the Atacama Desert and also includes the deserts south of the Ica Region in Peru.
Peru borders it on the north and the Chilean Matorral ecoregion borders it on the south. To the east lies the less arid Central Andean dry puna ecoregion. The drier portion of this ecoregion is located south of the Loa River between the parallel Sierra Vicuña Mackenna and Cordillera Domeyko. To the north of the Loa lies the Pampa del Tamarugal.
The Atacama is sparsely populated, with most towns located along the Pacific coast. In interior areas, oases and some valleys have been populated for millennia and were the location of the most advanced Pre-Columbian societies found in Chile. These oases have experienced little population growth and urban development. During the 20th century they have had conflicts over water resources with the coastal cities and the mining industry.
San Pedro de Atacama, at about 2,400 metres (8,000 ft) elevation, is like many of the small towns. Before the Inca empire and prior to the arrival of the Spanish, the extremely arid interior was inhabited primarily by the Atacameño tribe. They are noted for building fortified towns called pucarás, one of which is located a few kilometers from San Pedro de Atacama. The town's church was built by the Spanish in 1577.
The coastal cities originated in the 16th, 17th, and 18th centuries during the time of the Spanish Empire, when they emerged as shipping ports for silver produced in Potosí and other mining centers. During the 19th century the desert came under control of Bolivia, Chile, and Peru. With the discovery of sodium nitrate deposits and as a result of unclear borders the area soon became a zone of conflict and resulted in the War of the Pacific. Chile annexed most of the desert, and cities along the coast developed into international ports, hosting many Chilean workers who migrated there.
With the guano and saltpeter booms of the 19th century the population grew immensely, mostly as a result of immigration from central Chile. In the 20th century the nitrate industry declined and at the same time the largely male population of the desert became increasingly problematic for the Chilean state. Mineworkers and mining companies came into conflict, and protests spread throughout the region.
The Atacama Desert again became a source of wealth from the 1950s onwards, owing to copper mining. The Escondida and Chuquicamata porphyry copper mines are located within the Atacama Desert.
Inhabited towns in the desert include Copiapo, Vallenar, Huasco, Freirina, Caldera, Chanaral, Diego de Almagro, Chile, Taltal, Antofagasta, Calama, Chile, Tocopilla, and San Pedro de Atacama. In San Pedro de Atacama there is a marketplace for artisanal goods.
Most people who go to tour the sites in the desert stay in the town of San Pedro de Atacama. The Atacama Desert is in the top three tourist locations in Chile. The specially commissioned ESO hotel is reserved for astronomers.