El Alto (Spanish for "The Heights") is the second-largest city in Bolivia, located adjacent to La Paz in Pedro Domingo Murillo Province on the Altiplano highlands. El Alto is today one of Bolivia's fastest-growing urban centers, with an estimated population of 943,558 in 2020. It is also the highest major city in the world, with an average elevation of . The El Alto–La Paz metropolitan area, formed by La Paz, El Alto, Achocalla, Viacha, and Mecapaca, constitutes the most populous urban area of Bolivia, with a population of about 2.2 million. History The dry and inclement plain above La Paz was uninhabited until 1903 when the newly built railways from Lake Titicaca and Arica reached the rim of the canyon, where the La Paz terminus, railyards and depots were built along with a settlement of railway workers (a spur line down into the canyon opened in 1905). In 1925, the airfield was built as a base for the new air force, which attracted additional settlement. In 1939, El Alto's first elementary school opened. El Alto started to grow tremendously in the 1950s when the settlement was connected to La Paz's water supply (before this, all water had to be transported from La Paz in tanker vehicles) and building land in the canyon became more and more scarce and expensive. In an administrative reform in March 1985, the district of El Alto and its surroundings were politically separated from the City of La Paz (this date is officially referred to and celebrated as the city's "founding day"). In 1987, El Alto was formally incorporated as a city. In 1994, the city became the seat of the Roman Catholic Diocese of El Alto. Districts El Alto's autonomous government identifies 14 districts composing the city. Demographics El Alto is the largest city in Latin America with a mostly Indigenous population. About 76% of its inhabitants are Aymara, 9% are Quechua, 15% are Mestizo (descendants of Indigenous and Europeans), and less than 0.1% are Criollos (White). El Alto was once known as La Paz's bedroom community, though recent growth of commerce and industry has led some local authorities to claim the title of "Bolivia's Economic Capital." With this industrial growth, there is concern about water pollution by businesses, including tanneries and slaughterhouses, for the city and communities downstream. Rapid population growth means the city struggles to bring potable water and sewer service to parts