Mexico City

The city traces its origins to Tenochtitlan, founded by the Mexica people in 1325 on an island in Lake Texcoco. According to legend, the site was chosen when the Mexica saw a golden eagle perched on a prickly pear cactus devouring a rattlesnake — an image that endures on the Mexican flag. Over nearly two centuries, Tenochtitlan grew into the dominant city-state of Mesoamerica, with the Aztec Empire eventually reaching both the Gulf of Mexico and the Pacific Ocean.

Spanish explorer Hernán Cortés arrived at the city on 8 November 1519 and placed the Aztec ruler Moctezuma II under house arrest. After a violent uprising on the night of 30 June 1520 — known as La Noche Triste — Cortés regrouped and launched a siege that lasted from May to August 1521, during which smallpox and starvation devastated the population. Cuauhtémoc, the last Aztec ruler, surrendered in August 1521. Cortés then ordered the city rebuilt on the same site according to Spanish urban standards, and in 1524 the municipality of México Tenochtitlán was formally established.

During the colonial period, Mexico City served as the capital of New Spain, with the Viceroy residing in a palace on the main square, the Zócalo. The Catholic cathedral on the Zócalo was constructed over the ruins of the principal Aztec temple complex. The Zócalo itself, originally the Aztec ceremonial center, remained the symbolic heart of power throughout the colonial period and into the modern era.

The Spanish grid-plan city was built outward from the Zócalo, with colonists in the inner traza and indigenous residents in surrounding areas. Colonial Mexico City prospered through trade: unlike Peru or Brazil, it had access to both Atlantic and Pacific commerce. The city earned the nickname La Ciudad de los Palacios — the City of Palaces — attributed to the Prussian naturalist Alexander von Humboldt, who visited in the 19th century and wrote that Mexico City could rival any major city in Europe. Many of the opulent colonial palaces from the late 18th century still stand in the historic center.

The city suffered periodic flooding due to its location on drained lake beds. A massive labor draft — the desagüe — compelled thousands of indigenous workers over the colonial period to build and maintain drainage infrastructure.

Mexican independence from Spain was declared on 27 September 1821, and the Federal District was established shortly afterward as the seat of the new republic. The city served as the imperial capital on two occasions: the First Mexican Empire (1821–1823) under Agustín de Iturbide, and the Second Mexican Empire (1864–1867) under Maximilian I.

During the Mexican–American War (1847–1848), United States forces under General Winfield Scott captured the city following a series of engagements in September 1847. The assault included the storming of Chapultepec Castle, defended in part by military cadets who became celebrated in Mexican national memory as Los Niños Héroes (the Boy Heroes). The Treaty of Guadalupe Hidalgo was subsequently signed within what is now the northern part of the city.

The Mexican Revolution (1910–1920) left Mexico City relatively free of direct combat, though the Decena Trágica of February 1913 — a ten-day coup against president Francisco I. Madero — brought artillery fire to the city center and ended with Madero's forced resignation and murder.

In 1900 the city's population stood at roughly 500,000. Explosive growth in the mid-20th century transformed it into one of the world's largest metropolitan areas. The construction of Ciudad Universitaria — the main campus of the National Autonomous University of Mexico — in the mid-1950s marked a high point of modernist Mexican architecture; the campus, designed by architects including Mario Pani and featuring murals by Diego Rivera, David Alfaro Siqueiros, and José Chávez Morado, is now a UNESCO World Heritage Site.

The 1968 Olympic Games prompted major infrastructure investment in the city. In 1969, the Mexico City Metro — one of Latin America's most extensive urban rail systems — was inaugurated. By 1980, half of all industrial employment in Mexico was concentrated in the capital, and population growth had long since overflowed the Federal District into the adjacent State of Mexico. The 1985 earthquake, striking at 7:19 a.m. on 19 September and measuring approximately 8.1 on the Richter scale, caused enormous destruction and exposed severe government incompetence; citizen-led rescue and reconstruction efforts that followed became a turning point in Mexican civil society.

By the 1990s Mexico City had become notorious for severe air pollution, but sustained government programs — including vehicle emission inspections, fuel reformulation, and the introduction of bus rapid transit and bike-sharing — achieved dramatic reductions. Carbon monoxide levels fell sharply, and by 2014 sulfur dioxide and nitrogen dioxide were roughly one-third of their 1992 levels.

For most of the 20th century the head of government of Mexico City was appointed by the national president. In 1997 residents won the right to elect both the head of government and the members of the Legislative Assembly directly. Since then, left-wing parties — first the Party of the Democratic Revolution, later Morena — have held both offices. The city has adopted a range of progressive legislation including legal abortion, same-sex marriage, no-fault divorce, and legal gender change.

On 29 January 2016, the Federal District was officially renamed Ciudad de México (CDMX), granting the city greater constitutional autonomy while a specific clause prevents it from becoming a full state while remaining the national capital.

Mexico City sits in the Valley of Mexico, an enclosed basin in the Trans-Mexican Volcanic Belt with no natural drainage outlet. The valley floor is the former bed of Lake Texcoco, drained progressively from the 17th century onward. The city rests on heavily saturated lake-bed clay that is subsiding due to groundwater over-extraction: since the beginning of the 20th century the city has sunk by as much as nine metres in some areas, and continues to sink roughly 50 centimetres per year in affected zones. This subsidence complicates stormwater and wastewater management and leaves the city vulnerable to flooding during summer rains.

Surrounding mountains reach above 5,000 metres, including the volcanic peaks of Popocatépetl and Iztaccíhuatl to the southeast. The minimum altitude within the urban area is approximately 2,200 metres above sea level.

According to the 2020 census, the city proper had a population of 9,209,944 across 1,495 square kilometres, making it Mexico's primate city and the second-largest Spanish-speaking city proper in the world after Lima. Under the agreed definition of Greater Mexico City, the metropolitan area had a population of 21,804,515, ranking it the world's fifteenth-largest metropolitan area and the second-largest urban agglomeration in the Western Hemisphere after São Paulo. The informal demonym for Mexico City residents is chilango, historically used pejoratively by outsiders but widely embraced by residents themselves.

Mexico City is the oldest continuously inhabited capital in the Americas and one of only two capital cities in the Western Hemisphere founded by indigenous peoples. Its layered history — from Aztec island-city to Spanish viceregal seat to modern mega-metropolis — makes it one of the world's most historically significant urban centers. It remains the political, financial, and cultural heart of Mexico, hosting major international events across sport, business, and the arts.