Viceroyalty of the Río de la Plata The Viceroyalty of the Río de la Plata , ( ) , was the last and most short - lived Viceroyalty of the Spanish Empire in America . The Viceroyalty was established in 1776 out of several former Viceroyalty of Perú dependencies that mainly extended over the Río de la Plata Basin , roughly the present day territories of Argentina , Bolivia , Paraguay and Uruguay . Buenos Aires , located on the western shore of the Río de la Plata estuary , opposite the Portuguese outpost of Colonia del Sacramento , was chosen as the capital . Usually considered one of the late Bourbon Reforms , its creation was both motivated on commercial grounds ( Buenos Aires was by then a major spot for illegal trade ) , as well as on security concerns brought about by the growing interest some foreign powers had over the area , namely Great Britain and the Kingdom of Portugal . However , the Enlightening reforms proved counterproductive , or perhaps too late to quell the colonies ' demands . In fact , the entire existence of the Viceroyalty was characterised by growing unrest and instability . Between 1780 and 1782 , the Rebellion of Túpac Amaru II inspired a violent Aymara - led revolt across the Upper Peru highlands , evidencing the huge resentment towards colonial authorities from both mestizo s and indigenous populations . Twenty - five years later , two successive British attempts at conquering Buenos Aires and Montevideo were successfully repelled by Criollo - led defenses , enhancing their perceived autonomous capabilities as the Spanish troops were unable to help . In 1809 , the criollo elite revolted against colonial authorities at La Paz and Chuquisaca , establishing revolutionary Juntas . Albeit short - lived themselves , they provided some strong theoretical basis for the legitimacy of the " locally - based governing juntas " that proved decisive at the 1810 May Revolution events that deposed Viceroy Cisneros at Buenos Aires . The revolution spread all over the Viceroyalty , except for Paraguay ( which declared itself an independent nation in 1811 ) and the Upper Peru ( which remained controlled by royalist troops from Lima , and was eventually re - incorporated into the Viceroyalty of Peru ) . Meanwhile , the Governor of Montevideo Francisco Javier de Elío , appointed as a new Viceroy by the Cortes of Cádiz in 1811 , declared the Buenos Aires Junta seditious . However , after being defeated at Las Piedras he was only left in control of Colonia del Sacramento and Montevideo , so he returned to Spain on 18 November and resigned as Viceroy on January 1812 . By 1814 , as the patriots entered Montevideo , following a years - long siege , the Viceroyalty effectively ceased to exist . History . Origin and creation . In 1680 , Portuguese governor of Rio de Janeiro Manuel Lobo created the Department of Colonia and founded Colónia do Sacramento , a fort located in present Uruguay ' s coast and the department ' s capital . The main objective was to secure the Portuguese expansion of Brazil beyond the Treaty of Tordesillas that was rendered meaningless between 1580 and 1640 while Spain controlled Portugal . José de Garro quickly attacked and seized the fort for Spain , but on 7 May 1681 it was handed back to Portugal due to the Provisional Treaty of Lisbon . On the other hand , the Viceroyalty of Peru required all commerce to be performed through Lima ' s port , which restrained the Buenos Aires natural port potential economy , a problem that also caused large contraband activities in the region , especially in Asunción , Buenos Aires and Montevideo . Under these conditions , King Charles III of Spain issued a decree for the former Governor of the Río de la Plata Pedro Antonio de Cevallos creating the new viceroyalty , in August 1776 . The ruling found resistance in Lima , but was enforced anyway . The Cabildo of the Captaincy General of Chile requested the King not to be included into the new viceroyalty , which was accepted . However the Cuyo region with its main city Mendoza was split from the Captaincy General of Chile , something resented in Santiago since that region had been originally settled from Chile . The Portuguese prime minister Marquis of Pombal continued to encourage the occupation of territory which had already been awarded to the Spanish in the Treaty of Paris ( 1763 ) . King Charles III quickly reacted to the advantageous conditions : France was bound to be an ally as a guarantor of the treaty , and England due to its own colony problems couldn ' t help being neutral . Pedro de Cevallos would then conquer Colonia del Sacramento and the Santa Catarina islands after a siege of three days , which led to the First Treaty of San Ildefonso . With it , the Portuguese would retire from the Río de la Plata and leave the Banda Oriental for Spain , but in exchange Spain would leave for them the area of Rio Grande do Sul . Cevallos ends his military actions at this point and starts working with government , but was soon replaced by Juan José Vertiz y Salcedo . One of their first tasks was to promote local production of linen and hemp , to provide the Spanish cloth industries that the Bourbons sought to favor . The early viceroyalty . The conditions imposed by Spain to local commerce were high , but Charles III sought to reduce them a little . One such ruling allowed commerce as long as ships were Spanish and manned with Spanish naval officers . The ports of Buenos Aires and Montevideo were included in a list of Spanish ports allowed to commerce between themselves , certain Spanish American productions were free of taxes to enter Spain , and all the cities with ports would have Consulates or Tribunals of Commerce . This system wasn ' t a system of free trade yet , but it would be an antecedent of it . In the 1778 - 1788 period the commerce between Spain and Spanish America grew nearly 700 % . Buenos Aires would get its own customs in 1778 , and Montevideo in 1789 . Spanish policy aimed to truncate Argentina commerce and the Empire banned export of silver from Buenos Aires and tried to get all shipments out of Potosi . The system of corregimiento s to mark the subdivisions of the territory was ended in 1782 , and replaced with " Intendencias " by another ruling of Charles III . The new system was intended to re - enforce the royal authority and promote centralization . Buenos Aires had the main intendencia , and the other cities provincial ones . Cevallos reinstated in 1778 the Real Audiencia of Buenos Aires , but not moving back the one from Cochabamba but creating a new one . The Consulate of Commerce of Buenos Aires was ruled to be created the same year , but legal difficulties delayed its actual creation up to 1794 . In 1766 , Spain acquired the French colony on the Falkland Islands , called Port St . Louis , and after assuming effective control in 1767 , placed the islands under a governor subordinate to the Buenos Aires colonial administration . The expulsion of the British settlement brought the two countries to the brink of war in 1770 , but a peace treaty allowed the British to return from 1771 until 1776 with neither side relinquishing sovereignty . Decline . By the nineteenth century Buenos Aires was becoming more self - sufficient , producing about 600 , 000 cattle a year ( of which about one quarter was consumed locally ) , prompting the development of the area . But wars with Great Britain meant a great setback for the region ' s economy as maritime communications were practically paralyzed . The Alto Peru region started to show contempt as the expenses of administration and defense of the Río de la Plata estuary were mainly supported by the declining Potosí production . For instance , in the first years of the viceroyalty , around 75 % of the expenses were covered with revenues that came from the north . The Alto Plata ( mostly present Paraguay ) also had problems with the Buenos Aires administration , particularly because of the monopoly of its port on embarkations . The Napoleonic Wars preoccupied the Spanish government and , in time , resulted in Napoleon ' s placing his brother Joseph on the Spanish throne . By 1805 , Spain had to help France because of their 1795 alliance , and had lost its navy in the Battle of Trafalgar , but the Spanish prime minister had warned the viceroyalty of the likelihood of a British invasion , and that in such an event the city of Buenos Aires would be on its own . On 27 June 1806 , a small British force of around 1 , 500 men under Col . William Carr Beresford successfully invaded Buenos Aires after a failed attempt to stop him from viceroy Rafael de Sobremonte , who fled to Córdoba . The British forces were thrown back by the " criollos " on December 1806 , a militia force from Montevideo under the leadership of Santiago de Liniers . In February 1807 , British reinforcements of about 8 , 000 men under Gen . Sir Samuel Auchmuty captured Montevideo after a fierce fight , and in May Lt . Gen . John Whitelock arrived to take overall command and attacked Buenos Aires on 5 July 1807 . After losing more than half his force killed and captured , Whitelock signed a cease - fire and left for Great Britain . Thus , lack of support from Spain and the confidence - boost by the fresh defeat of a world power prompted a movement towards independence at the expense of the viceroyalty . As of 1814 , Argentina had been self - governed for about four years , and Paraguay had already declared its independence , and the viceroyalty was effectively dissolved when the rebel troops entered Montevideo after a years - long siege . Government . The Viceroyalty of the Río de la Plata was a viceroyalty created in 1776 by the Spanish king Charles III of Spain . Although it functioned as a Spanish colony , Río de la Plata was technically a personal possession of the King of Spain . This allowed both European Spain and its overseas territories to have their own laws and regulations . List of viceroys . The King of Spain appointed viceroys to govern in his name . In the beginning their terms had no fixed duration and may last for life , but afterwards they were shortened to periods of 3 to 5 years . Because of the distances between Spain and America , and the means of transport available in that age , there were long delays between the designation of a viceroy and the viceroy ' s effectively taking power .