In 1790, upon the signature of the Treaty of San Lorenzo del Escorial, Great Britain undertook not to establish any settlements on either the Eastern or the Western coasts of South America or on the adjacent islands already occupied by Spain, with was the case of the Malvinas Islands. Spain appointed a succession of 32 governors until 1811, when the garrison at Puerto Soledad was required from Montevideo to defend the Monarchy at the beginning of the War of Independence. The first autonomous government of the United Provinces of the River Plate referred to the Malvinas Islands in various administrative acts. Malvinas were integral part of their territory, inherited from Spain by succession of States under the utis possidentis juris principle of 1810.
Officer Jewett took possession of the Malvinas Islands on behalf of the United Provinces of the River Plate at a public ceremony in Puerto Soledad, which was attended by sealers and whalers of different nationalities. There was no official comment from Great Britain, as Argentina´s possession was public, effective and peaceful.
In 1829, the Duke of Wellington stated: “I have perused the enclosed papers respecting the Falkland Islands. It is not clear to me that we have ever possessed the sovereignty of all those islands. The Convention certainly goes no further than to restore to us Port Gumont, which we abandoned nearly sixty years ago.”
In reality, Great Britain never possessed the totality of the archipelago.
Argentina´s officials had never had any doubt that the islands belong to Argentina. During the XIX century, Argentina´s maps reflected Argentina´s sovereignty over the islands. Among others, the 1882 Latzina Map depicts the islands as “Islas Malvinas” and part of Argentina. The islands are colored in the same pale beige used for Buenos Aires (this map depicts different opportunities for immigrants; regions apt for farming in whole Argentine territory are depicted with different shades of color). In 1886, Argentina´s Geographical Institute published a map depicting Tierra del Fuego Governance which included Malvinas. In 1918, the islands are presented as “Islas Malvinas” and hence part of Argentina on a map issued by the Agricultural Ministry that depicted the whole Argentine territory in different shades and colors according to degree of agricultural development and availability of railroad networks.