Created in 1776, the Viceroyalty of the Río de la Plata was the last and most shortlived viceroyalty created by Spain. (The Spanish name, Virreinato del Río de la Plata, translates literally to Viceroyalty of the River of Silver, although some sources conventionally call the viceroyalty Viceroyalty of the River Plate; see the Encyclopædia Britannica entry.)
Its limits roughly contained the territories of present Argentina, Bolivia, Paraguay and Uruguay. The Captaincy General of Chile was part of the Viceroyalty of Peru. It was mainly created because of security concerns on the increasing interest of other world powers on the area, mainly Portugal and Great Britain.

Origin and creation
See also: Government of the Río de la Plata.
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.
Cevallos sent a warning and started aggressions against Santa Catalina, from where the Portuguese had already fled, and it was conquered in less than a month with no casualties. Then Cevallos sailed towards Montevideo and with the aid of Buenos Aires governor Vértiz reclaimed Colonia, also without resistance. Cevallos advanced to Maldonado city, where he stopped his advance towards the Rio Grande, as he was informed of the Treaty of San Ildefonso which ended hostilities in the area.
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.
Cevallos was then free of other matters and started significant transformations in the area, including free commerce (established on September 6, 1777) with the aid of the Potosí minerals which were meant to be the viceroyalty's main source of revenue. The Bourbonic reforms in 1778 also helped greatly with the region's development, and between 1792-1796 there was an unprecedented boom.