[8] Buenos Aires, located on the western shore of the Río de la Plata estuary flowing into the Atlantic Ocean, opposite the Portuguese outpost of Colonia del Sacramento, was chosen as the capital.

Usually considered one of the late Bourbon Reforms, the organization of this viceroyalty was motivated on both 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 of competing foreign powers in the area.

Between 1780 and 1782, the Rebellion of Túpac Amaru II inspired a violent Aymara-led revolt across the Upper Peru highlands, demonstrating the great resentment against colonial authorities by both the mestizo and indigenous populations.

In 1809, the Criollo elite revolted against colonial authorities at La Paz and Chuquisaca, establishing revolutionary governments or juntas.

Although short-lived, retroversion of the sovereignty to the people provided a theoretical basis for the legitimacy of the locally based governments (temporarily in the absence of a legitimate king in Spain).

The name "Provincias del Río de la Plata" was formally adopted in 1810 during the Cortes of Cádiz to designate the Viceroyalty [6] based on popular sovereignty.

Meanwhile, the Governor of Montevideo Francisco Javier de Elío, appointed as a new Viceroy by the Spanish Government in 1811, declared the Buenos Aires Junta seditious.

The Viceroyalty was disestablished in 1825 as Spanish political entity with the fall of Upper Peru and the death of the last Viceroy Pedro Antonio Olañeta.

[9] In 1680, Manuel Lobo, Portuguese governor of Rio de Janeiro, created the Department of Colonia and founded Colónia do Sacramento.

Lobo's chief objective was to secure the Portuguese expansion of Brazil beyond the 1494 Treaty of Tordesillas, which had defined areas of influence in the Americas between the Iberian nations.

This policy failed to develop the potential of Buenos Aires as an Atlantic port, adding months to the transport of goods and commodities in each direction.

The Portuguese prime minister, Marquis of Pombal, encouraged the occupation of territory which had already been awarded to the Spanish in the Treaty of Paris (1763), following the British defeat of France in the Seven Years' War.

Pedro de Cevallos conquered Colonia del Sacramento and the Santa Catarina islands after a siege of three days, gaining the First Treaty of San Ildefonso.

Cevallos ended his military actions at this point and started working with government, but he was soon replaced by Juan José Vertiz y Salcedo.

The viceroyalty was tasked with promoting local production of linen and hemp as export commodity crops, to supply the Spanish cloth industries that the Bourbons sought to favor.

The expulsion of the British settlement in 1770 brought the two countries to the brink of war but a peace treaty was offered by Spain "to restore the port and fort called Egmont, with all the artillery and stores, according to the inventory" which was accepted by Britain.

The Spanish prime minister had warned the viceroyalty of the likelihood of a British invasion, saying it could not provide support to the city of Buenos Aires.

The criollo bourgeoisie aspirations in the face of lack of support from Spain and the defeat of a world power by local forces added to their confidence and fueled their movement toward independence.