Buenos Aires, officially the Buenos Aires Province, is the largest and most populous Argentine province. It takes its name from the city of Buenos Aires, the capital of the country, which used to be part of the province and the province's capital until it was federalized in 1880. Since then, in spite of bearing the same name, the province does not include Buenos Aires city, though it does include all other parts of the Greater Buenos Aires metropolitan region, which include approximately three-fourths of the conurbation's population. The capital of the province is the city of La Plata, founded in 1882.
It is bordered by the provinces of Entre Ríos to the northeast, Santa Fe to the north, Córdoba to the northwest, La Pampa to the west, Río Negro to the south and west and the Autonomous City of Buenos Aires to the northeast. Uruguay is just across the Rio de la Plata to the northeast, and both are on the coast of the Atlantic Ocean to the east. Almost the entire province is part of the Pampas geographical region, with the extreme south often considered part of the Patagonia region.
The province has a population of about 17.5 million people, which is 38% of Argentina's total population. The province covers an area of , which is about 11% of Argentina's total area and makes it the country's largest province.
History
thumb|left|200px|Governor [[Juan Manuel de Rosas (1841 oil portrait by Cayetano Descalzi) ruled until 1852 with an iron fist and kept the fragile Confederation under the tutelage of Buenos Aires Province]]
The inhabitants of the province before the 16th-century advent of Spanish colonization were aboriginal peoples such as the Charrúas and the Querandíes. Their culture was lost over the next 350 years. They were subjected to Eurasian plagues from which few survived. The survivors joined other tribes or have been mostly absorbed by Argentina's European immigration.
Pedro de Mendoza founded Santa María del Buen Ayre in 1536. Even though the first contact with the aboriginals was peaceful, it soon became hostile. The city was evacuated in 1541. Juan de Garay re-founded the settlement in 1580 as Santísima Trinidad y Puerto Santa María de Los Buenos Aires.
Amidst ongoing conflict with the aboriginals, the cattle farms extended from Buenos Aires, whose port was always the center of the economy of the territory. Following the creation of the Viceroyalty of the Río de la Plata at the end of the 18th century, the export of meat, leather and their derivatives through the port of Buenos Aires was the basis of the economic development of the region.
Jesuits unsuccessfully tried to peacefully assimilate the aboriginals into the European culture brought by the Spanish conquistadores. A certain balance was found at the end of the 18th century when the Salado River became the limit between both civilizations, despite frequent malones (aboriginal attacks on border settlements). The end to this situation came in 1879 with the Conquest of the Desert (Conquista del Desierto) in which the aboriginals were almost completely exterminated.
thumb|left|200px|1 [[Decimo (coins)|decimo coin minted for the province in 1822. The reverse features the provincial coat of arms]]
After the independence from Spain in 1816, the city and province of Buenos Aires became the focus of an intermittent Argentine Civil War with other provinces. A Federal Pact secured by Governor Juan Manuel de Rosas in 1831 led to the establishment of the Argentine Confederation and to his gaining the sum of public power, which provided a tenuous unity. Ongoing disputes regarding the influence of Buenos Aires, between Federalists and Unitarians, and over the Port of Buenos Aires (the prime source of public revenue at the time) fueled periodic hostilities. The province was declared independent on 11 September 1852, as the State of Buenos Aires. Concessions gained in 1859 Pact of San José de Flores and a victory at the Battle of Pavón led to its reincorporation into the Argentine Republic on 17 December 1861. Intermittent conflicts with the nation did not truly cease until 1880, when the city of Buenos Aires was formally federalized and, thus, administratively separated from the province.
thumb|right|Period illustration of the 1882 placement of La Plata's [[foundation stone]]
La Plata was founded in 1882 by Governor Dardo Rocha for the purpose of becoming the provincial capital. The equivalent of a billion (1880s) dollars of British investment and pro-development, education and immigration policies pursued at the national level subsequently spurred dramatic economic growth. Driven by European immigration and improved health, the province's population, like Argentina's, nearly doubled to one million by 1895 and doubled again by 1914. Rail lines connected nearly every town and hamlet in the province by 1914; many developed around the new railway stations.
This era of accelerated development was cut short by the Wall Street crash of 1929, which caused a sharp drop in commodity prices (99% of Argentine exports were agricultural) and led to a halt in the flow of investment funds between nations. The new Concordance and Perón governments funded ambitious lending and public works programs, visible in Buenos Aires Province through the panoply of levees, power plants, water works, paved roads, municipal buildings, and (particularly during Perón's 1946–55 tenure) schools, clinics and massive regional hospitals.
The province's population, after 1930, began to grow disproportionately quickly in the suburban areas of Buenos Aires. These suburbs had grown to include 4 million out of the province's total 7 million people in 1960. Of these, about a million still live with seriously compromised water quality, despite the province's (sometimes counterproductive) efforts to remedy the issue.
Contemporary history
In April 2013, the northeastern section of Buenos Aires Province, particularly its capital, La Plata, experienced several flash floods that claimed the lives of at least 89 people.
Alejandro Armendáriz, of the Radical Civic Union, was elected governor in 1983, when Raúl Alfonsín became president. Alfonsín lost the 1987 midterm elections, leading to the victory of Antonio Cafiero. From then to 2015, all governors have been Peronists. The high population of the province makes it highly influential in Argentine politics. With both ruling for two terms, the rivalry of the president Carlos Menem and governor Eduardo Duhalde dominated the Argentine politics during the nineties. A similar case took place with the president Cristina Fernández de Kirchner and governor Daniel Scioli. María Eugenia Vidal, from Republican Proposal, won the 2015 elections, and became the first female governor of the province.
Paleontology
In February 2021, researchers led by paleontologist Nicolás Chimento of the Museo Argentino de Ciencias Naturales announced the discovery of a well-preserved fossilized skull of the giant ground sloth Megatherium near San Eduardo del Mar, Province of Buenos Aires. According to paleontologists, the fossil belonged to a juvenile and dated back approximately 3.58 million years.
Government
thumb|Provincial Government House in La Plata
thumb|Provincial [[Legislature of Buenos Aires Province|Legislature in La Plata]]
thumb|Federal courts in La Plata
The provincial government is divided into three branches: the executive, headed by a popularly elected governor, who appoints the cabinet; the legislative (represented by the Legislature, which is split into the Chamber of Deputies and the Senate); and the judiciary, headed by the Supreme Court.
The Constitution of Buenos Aires Province forms the formal law of the province.
In Argentina, the most important law enforcement organization is the Argentine Federal Police, but the province is policed by its own Buenos Aires Provincial Police.
Geography
Buenos Aires Province, at , is slightly bigger than Italy. The landscape is mainly flat, with two low mountain ranges: Sierra de la Ventana (near Bahía Blanca) and Sierra de Tandil (Tandil). The highest point is Cerro Tres Picos ( amsl; ) and the longest river is Río Salado ( long).
As part of The Pampas, the weather of the province is strongly influenced by the ocean, with hot summers and temperate winters. Humidity is high and precipitation is abundant and distributed over the year. The Western and Southwestern regions are drier and are part of the Semi-arid Pampas ecoregion. The southernmost part of the province is often included in definitions of the Patagonia region.
<div class="center">
{|
|-
|valign="top"|
thumb|210px|The [[Sierra de la Ventana (mountains)|Sierra de la Ventana]]
|valign="top"|
thumb|210px|The Arias Canal in the [[Paraná Delta]]
|valign="top"|
thumb|210px|Al Este Bodega y Viñedos in [[Medanos (appellation)|Médanos, located on the southern tip of Buenos Aires Province away from Bahía Blanca]]
|valign="top"|
|}
</div>
Climate
thumb|Köppen climate map of Buenos Aires
thumb|Snow on La Perla beach, [[Mar del Plata (1991)]]
The climate of the province of Buenos Aires is extremely benign for human activities: it is temperate, with four marked seasons and reliable rainfall on most regions. The province can be divided into four main climatic regions: the southwestern, drier region; the cool Atlantic region; the northern and eastern humid region, and the Delta region, with the warmest, wettest climate.
The northern region has warm, humid summers, with days between and nights between , pleasant falls, cool, drier winters with highs between and nights between , and windy, variable springs. Heat waves may bring days with temperatures over , but these do not usually last very long, as cold fronts bring thunderstorms and cooler days, with night temperatures often falling down to . Winter cold waves may bring days with highs about , and lows below , with extremes down to . Snow is uncommon, but there have been accumulations on several occasions in the past. Precipitation ranges from per year.
The Delta region is slightly warmer, especially at night, due to the presence of water and the northerly location. Summer nights tend to be stickier, and winters can be damp and foggy, with most nights between . Frost is still to be expected, but temperatures will almost never fall below , and snow has fallen only twice in the last century. Precipitation ranges from and falls throughout the year. The city of Buenos Aires is surrounded by a climate similar to the northern part of the province, but the city itself resembles more the Delta climate, with less frost.
The southwestern region is the driest region, and it experiences a more marked differences in temperatures. Summers are often hot, between , but nights are usually comfortable (). Thunderstorms are less frequent but can be very violent in nature. Frost can make an appearance as early as March, but usually first comes in April. Winters are cool and dry, with days between and nights between . Frost occurs on an almost daily basis, with temperatures below not uncommon, and down to recorded in some areas. Snowfall may occur every once in a while, but accumulations are usually small. Total precipitation ranges from , with slightly rainier springs and falls.
The Atlantic region sees very moderate weather: the ocean is cold ( in the summer) and sea breezes often bring chilly weather until midsummer. The hottest months average with nights between , providing a perfect relief for the inhabitants of the hotter interior. Fall is often rainy, and winters can be windy and chilly: temperatures average from , and nights from . There can be long periods of drizzly weather and constant temperatures of about . Frost is common but temperatures will rarely fall below , and snowfalls sometimes, but accumulations are only to be expected every few years. Precipitation ranges from . The Sierras de la Ventana (up to ) experience cooler weather, especially at night.
The geography of the province is crossed by occasional west Pampero winds. The southern Sudestada produces storms and temperature drops, most notably the Santa Rosa storm, which takes place every year almost exactly on 30 August.
Administrative divisions
thumb|right|Boundaries of the 135 partidos of Buenos Aires Province
Unlike the other provinces of the country, in the province of Buenos Aires, the territorial divisions are called partidos, instead of departments.
These also constitute the municipal division of the province. The provincial Constitution does not recognize the municipal autonomy that was recognized for the whole country in the reform of the National Constitution of 1994. Each partido corresponds to a municipality and is governed by a mayor (intendente) elected by popular vote. The process of creating a partido is much more dynamic than in the other provinces, with a total of six more partidos in 2000 than in 1990. Most of the newer partidos were created in the Greater Buenos Aires. There are 135 partidos, the last established by law is Lezama (2009).
Demographics
Population
Buenos Aires Province is the most populated province of the country. The INDEC estimates that the population of Buenos Aires Province was 17,541,141 on 1 July 2020, a 12.26% increase since the 2010 national census. According to that census, there were 15 million inhabitants (38% of the national population), of which 12 million lived in Greater Buenos Aires and 3 million in the rest of the province. Around 33.8% of the inhabitants weren't born in the province, of whom 3,918,552 are migrants from other provinces and 758,640 were born abroad.