Since 1880, when it was separated from its province and made federal territory, Buenos Aires has been the capital of Argentina. It is also the country’s largest city, standing on the southwestern shore of the Río de la Plata estuary where the pampas meet the water. The 2022 census counted 3,121,707 people in the Autonomous City itself, a district of just under 206 square kilometres, and about 16 million in the wider metropolitan area, one of the largest in the Americas. What sets it apart is how clearly its streets record each era it has lived through, from a failed 16th-century camp to a self-governing autonomous city.
1536–1541: Pedro de Mendoza’s Santa María del Buen Ayre
The first European to reach the estuary was Juan Díaz de Solís, sailing for Spain in 1516; he was killed by the Charrúa on the far shore, in what is now Uruguay. Twenty years later, on 2 February 1536, an expedition under Pedro de Mendoza founded the Ciudad de Nuestra Señora Santa María del Buen Ayre on a spot inside today’s San Telmo district. The name honoured Our Lady of Bonaria, the Virgin of Fair Winds venerated by sailors in Sardinia and Seville, a story told in full in our piece on the origin of the name Buenos Aires.
Mendoza’s settlement did not last. Repeated attacks by the Indigenous peoples of the area forced the settlers away, and the site was abandoned in 1541 (some accounts give 1542).
1580–1776: Juan de Garay’s Port of Contraband
The permanent city came from the north. On 11 June 1580 Juan de Garay, who had sailed down the Paraná River from Asunción, refounded it as the Ciudad de la Santísima Trinidad y Puerto de Santa María del Buen Aire. The short form Buenos Aires came into common use during the 17th century. A fort was raised at the waterfront in 1594 and replaced in 1713 by the masonry Castle of San Miguel, on the ground where the Casa Rosada now stands.
For most of the colonial period the city was a backwater by law. Spanish trade was forced through Seville and then Lima, so legal goods reached Buenos Aires only after a long overland journey and heavy taxes. The porteños, as the port’s people came to be called, answered with contraband, much of it with the Portuguese across the river, and the habit bred lasting resentment of Spanish authority.
1776–1816: Viceroyalty, British Invasions and the May Revolution
Charles III of Spain changed the rules. In 1776 he carved the Viceroyalty of the Río de la Plata out of the Viceroyalty of Peru, covering roughly present-day Argentina, Uruguay, Paraguay, Bolivia and northern Chile, with Buenos Aires as its capital, and he later opened the port to wider trade. The city had gone from smuggling outpost to seat of a viceroy in a single reign.
Then came two British attacks. In 1806 a British force took the city and the viceroy, Rafael Sobremonte, fled to Córdoba; an army from Montevideo led by Santiago de Liniers retook it. A second British invasion in 1807 was repelled. The local militias raised to fight the British shifted power toward the American-born criollos, and in May 1810 they backed the removal of Viceroy Baltasar Hidalgo de Cisneros. The May Revolution began the war of independence, which was formally declared at the Congress of Tucumán in 1816. A year after the revolution, in 1811, the Primera Junta ordered the Pirámide de Mayo, now the oldest national monument in the city.
1820–1880: Porteños Against the Provinces
Independence did not settle who should rule. Buenos Aires, liberal and free-trading, stood against provinces to its northwest that favoured a more nationalist and Catholic politics, and the centralist-federalist conflict ran through much of the century. The city also faced outside pressure: a French naval blockade from 1838 to 1840 and an Anglo-French one from 1845 to 1848 both failed to force the Argentine government to terms.
From 1853 to 1860 the city was capital of a breakaway State of Buenos Aires, separate from the Argentine Confederation. The question was fought over more than once on the battlefield until 1880, when the city was federalised and detached from Buenos Aires Province, which built a new capital for itself at La Plata, founded in 1882. From then until 1996 the president appointed the city’s mayor. For how Argentina’s other provinces arranged their seats of government, see our list of Argentina’s province capitals.
1880–1930: Federal Capital and the Immigrant City
The next half-century made the city most visitors recognise today. Railways brought the produce of the pampas to its docks, and Eduardo Madero’s new port was built between 1887 and 1897. In 1888 Law 2089 enlarged the federal capital by annexing the towns of Belgrano and Flores. Plaza de Mayo took its present form in 1884, when a colonnade that had split the old main square was demolished.
Above all, people arrived. Between 1887 and 1915 the city’s population tripled from about 500,000 to 1.5 million, mainly through immigration from Italy and Spain. Italian arrivals, many speaking Neapolitan, Sicilian or Genoese, mixed their dialects with Spanish into a pidgin called cocoliche, and a CONICET and University of Toronto study found that porteño speech melody is closer to Neapolitan than to any other language. La Boca, by the old port, filled with settlers from Liguria and became an early home of tango.
The money showed in stone. The Teatro Colón opened on 25 May 1908 with Verdi’s Aida and grew into one of the world’s leading opera houses. In 1913 the first Subte line opened, the oldest underground railway in the Southern Hemisphere and the Spanish-speaking world. The early 20th century also brought South America’s tallest buildings, and conditions in the crowded conventillos, the tenements where many immigrants lived, fed high rates of tuberculosis.
1930–1983: Peronism, the Obelisco and the Dictatorship
The 1930s opened a new chapter in concrete. The Obelisco, 67.5 metres tall, was put up in 1936, its builders finishing their work in just 31 days, to mark 400 years since Mendoza’s founding, at the crossing of Corrientes Avenue and the planned Avenida 9 de Julio. That avenue had first been proposed in 1888 but was resisted by landowners for decades; work began in 1935, its first section opened on 12 October 1937, and the main stretch was finished only in the 1960s. At about 110 metres across, it is often called the widest avenue in the world.
Migrants now came from Argentina’s own provinces and neighbouring countries, and shanty towns called villas miseria grew around the industrial districts from the 1930s. These workers became the base of Peronism, born in the mass rally of 17 October 1945 in the Plaza de Mayo. On 16 June 1955 a faction of the navy bombed the Plaza de Mayo area, killing 364 civilians, the only air attack the city has suffered; President Juan Perón was overthrown three months later.
The 1970s brought political violence and, after the March 1976 coup led by General Jorge Videla, a military dictatorship during which thousands of people were abducted and disappeared; human rights organisations put the number as high as 30,000. The silent marches of their mothers in the square, the Mothers of the Plaza de Mayo, became one of the defining images of the period. The regime’s appointed mayor, Osvaldo Cacciatore, drew up a network of eight urban freeways; only three were built, as elevated roads that still cut through residential neighbourhoods.
1983–1996: Democracy, Two Bombings and Autonomy
The return of democracy in 1983 coincided with a cultural revival, and the 1990s brought a boom in construction and finance. The derelict docks of Puerto Madero were handed on 15 November 1989 to a joint federal-city company, the Corporación Antiguo Puerto Madero, and their brick warehouses were turned into offices, lofts, universities and restaurants, with towers rising on the eastern side after the Hilton opened in 1999.
The same years brought terror. On 17 March 1992 a bomb destroyed the Israeli embassy, killing 29 people, and on 18 July 1994 an explosion at a building housing Jewish community organisations killed 85. That same year the constitutional reform of 1994 granted the city autonomy and ended the president’s right to appoint its mayor. On 30 June 1996 voters elected their first head of government, Fernando de la Rúa, who went on to be president of Argentina from 1999 to 2001.
1996–Today: The Autonomous City and 3.1 Million Porteños
Officially the Ciudad Autónoma de Buenos Aires, or CABA, the city is neither part of Buenos Aires Province nor its capital. It has its own constitution, a head of government and a legislature elected by proportional representation, and since 2007 it has been divided into communes run by elected seven-member boards. Its politics have been turbulent at times: Aníbal Ibarra was removed from office on 6 March 2006 after the República Cromañón nightclub fire. Mauricio Macri won in 2007 and went on to the presidency, Horacio Rodríguez Larreta followed in 2015, and Jorge Macri took office in December 2023.
The city still lives on its old grid of 110-metre manzana blocks, crossed by the 35-kilometre Rivadavia Avenue and the theatre strip of Corrientes. Its climate is humid subtropical, with about 1,258 millimetres of rain a year; snow is so rare that the fall of 9 July 2007 was the first major snowfall in 89 years. The waters that brought Mendoza’s ships still shape its edges, and the river system behind them is traced in our guide to the La Plata river basin.
Quick Facts About Buenos Aires
- Country: Argentina
- Continent: South America
- Country population: approximately 46.0 million
- Capital city status: Buenos Aires is the capital of Argentina, the seat of national government, and the location of foreign embassies, parliament, and the head of state's official residence.
Frequently Asked Questions
What is the capital of Argentina?
The capital of Argentina is Buenos Aires. Buenos Aires is the seat of national government, hosts most foreign embassies and consulates, and is typically where the head of state and parliament are located.
What continent is Buenos Aires in?
Buenos Aires, the capital of Argentina, is located in South America. As Argentina's capital, Buenos Aires serves as the country's primary connection to the broader South American political, economic, and cultural sphere.
Why is Buenos Aires the capital of Argentina?
Buenos Aires was chosen as the capital of Argentina for reasons that typically combine geography, history, and politics. Capital city selections often reflect a desire for centrality (being accessible from across the country), historical importance (being a longstanding seat of government or culture), or neutrality (being acceptable to multiple regions or ethnic groups within the country). The specific reasons for Buenos Aires's designation are detailed in the city's history above.
What is Buenos Aires known for?
As the capital of Argentina, Buenos Aires is best known for housing the country's central government institutions — parliament, presidential or royal residences, supreme court, and key ministries. It is also typically a major cultural and economic center within Argentina, hosting national museums, embassies, and signature monuments. The introduction and history sections above provide detailed coverage of the city's specific notable institutions and landmarks.
Related Pages
- Argentina Country Guide — full geography, climate, economy, and culture overview
- Flag of Argentina — meaning, history, and design of Argentina's national flag