Treaty of Madrid Summary

  • Last updated on November 10, 2022

The Treaty of Madrid altered the boundary between Portuguese and Spanish South America, formally recognizing that some lands on the western, Spanish side of the original boundary had already become de facto possessions of Portugal. Subsequent treaties reversed and modified the Madrid agreements.

Summary of Event

In 1494, Pope Alexander VI authorized a division of all territories yet to be discovered in the New World between Spain and Portugal. In the Treaty of Tordesillas, Tordesillas, Treaty of (1494) a line of demarcation along a north-south axis was drawn that, in South America, allotted territory east of the mouth of the Amazon River to Portugal and west of the river’s mouth to Spain. Over the course of the following centuries, the Brazilian frontier Frontier;Brazilian advanced steadily westward, following the course of the continent’s rivers and terrain, which roll steadily down to the Amazon and Plata river systems. Portuguese settlement thereby penetrated beyond the Tordesillas boundary. This settlement accelerated in the eighteenth century after gold was discovered in the interior of Brazil. Spain and Portugal were thus prompted to negotiate their boundaries in South America more definitively. [kw]Treaty of Madrid (1750) [kw]Madrid, Treaty of (1750) Madrid, Treaty of (1750) Treaties;European Spanish South America Portuguese South America Territory distribution;South America Madrid, Treaty of (1750) [g]Spain;1750: Treaty of Madrid[1300] [g]Portugal;1750: Treaty of Madrid[1300] [g]Brazil;1750: Treaty of Madrid[1300] [g]Argentina;1750: Treaty of Madrid[1300] [g]Paraguay;1750: Treaty of Madrid[1300] [g]Uruguay;1750: Treaty of Madrid[1300] [c]Diplomacy and international relations;1750: Treaty of Madrid[1300] [c]Expansion and land acquisition;1750: Treaty of Madrid[1300] Carvajal y Lancáster, José de Ferdinand VI Gusmão, Alexandre de John V Joseph I (1714-1777) Pombal, marquês de

Portugal wished to consolidate its hold over the entirety of the Amazon River Basin, which extended across northern Brazil. Beyond the southern edge of Brazil, Portugal held a trading and military outpost, Colônia do Sacramento, on the left bank of the Plata River, that it was willing to cede to Spain. By giving up their claims to the Plata, the Portuguese believed they would free themselves to concentrate on the Amazon. Spain, for its part, wished to acquire Colônia do Sacramento in order to consolidate its hold over the Plata system and to suppress the smuggling of Spanish silver from Bolivia that was conducted through the port. However, to ensure that southern Brazil was protected from future Spanish incursions, Portugal sought possession of the territory of seven Spanish Jesuit Jesuits;South America missionary villages that bordered the region. These villages, populated by South American Indians and Jesuit priests, lay on the left bank of the Uruguay River, and Portugal wanted them vacated and transferred to the right bank.

On January 13, 1750, Portugal and Spain signed the Treaty of Madrid, Madrid, Treaty of (1750) a document with significant historical and legal consequences. Negotiating for Spain was José de Carvajal y Lancáster, chief royal minister and head of the Council of the Indies. For Portugal, Alexandre de Gusmão, the Brazilian-born secretary and adviser to King John V, conducted negotiations. Encouraging them were King Ferdinand VI of Spain and his Portuguese wife, Queen Barbara.

The Madrid document began by abrogating the Treaty of Tordesillas, which had divided the Americas in a straight line along an arbitrarily chosen line of longitude. With that boundary abolished, the new boundaries of Spanish and Portuguese America could be determined based on natural geographical contours, as well as on the current occupation of territory by the colonists of the two nations. The major part of the Amazon valley was occupied, albeit sparsely, by the Portuguese. The Plata was primarily Spanish. Thus, it made sense for the Portuguese to lay claim to the valley, which was already their territory de facto, and to abandon their outpost at Colônia do Sacramento, since it stood in de facto Spanish territory. To protect southern Brazil, the Seven Missions complex would be dismantled and their occupants moved beyond the Uruguay River. Both parties agreed to this arrangement and the treaty was signed.

No sooner had the treaty been completed, however, than conditions arose that mitigated its execution. John V died, and Joseph I ascended the Portuguese throne. The new king’s foreign minister, Sebastião José de Carvalho e Mello, was in charge of executing the terms of the Treaty of Madrid, but he was opposed to the treaty. Carvalho e Mello, deeply suspicious of the Jesuits, did not believe the Spanish would abandon the Seven Missions region. He therefore delayed ordering the Portuguese evacuation of Colônia do Sacramento. This inaction aroused Spanish suspicions. Moreover, Carvalho e Mello believed in strict adherence to uti possidetis, Uti possidetis (territory claims) the principle that occupied territory should belong to the power that occupied it. He favored continued Portuguese expansion into any territory it could occupy and opposed ceding any territories the nation had already acquired. He therefore found surrender of the settled territories of Colônia do Sacramento and the Seven Missions to a contradiction of the treaty’s guiding principle.

Spanish and Portuguese surveyors and cartographers had been dispatched to determine the new colonial borders. The southern contingent was met, however, with Indian resistance near the Seven Missions territory. The Amazon contingent never departed. Amid mutual suspicion, delays, and conflicts, Carvalho e Mello engineered a new agreement. The Treaty of El Pardo El Pardo, Treaty of (1761) was signed on February 12, 1761, annulling the Madrid document.

Not until Carvalho e Mello’s exit from office were the continuing territorial conflicts in the Plata region Plata region, South America resolved. By the Treaty of San Ildefonso, San Ildefonso, Treaty of (1777) signed on October 1, 1777, Portuguese territory was recognized as extending to Rio Grande (today the southern tip of Brazil). Spanish territory included both the Seven Missions and Colônia do Sacramento. Nonetheless, during the beginning of the following century, Portugal reclaimed both territories—it would only be able to hold the Seven Mission region permanently, however.


Despite the subsequent abrogation of the Treaty of Madrid, its historic application of the international legal principle of uti possidetis became the basis for resolving territorial disputes between Brazil and the many Spanish American countries that it bordered. The natural contours of Brazil’s terrain and rivers determined the flow of its people into the interior. For this reason, by the end of the seventeenth century, Brazilians had already occupied much of the territory of present-day Brazil, whose borders are based largely on natural geographical limits. However, only by the end of eighteenth century was there legal recognition of these limits, demarcated in final detail in treaties signed at the beginning of the twentieth century.

With Brazil’s southern tip now lying as far as Rio Grande, the country extended into the northern edge of the pampas (savannah) of what would become Argentina and the cattle-raising culture of the gaucho cowboys (gaúcho in Portuguese) who lived there. The southern border of Brazil became one of the most fortified regions in the country, and it would be the one area of Brazil that witnessed significant warfare with its neighbors.

Nonetheless, neither Brazil nor Argentina would dominate the east bank of the Uruguay River. Rather, this region became the country of Uruguay, essentially a buffer state between giant neighbors. However, insofar as Brazil extended southward to the Uruguay River and controlled the headwaters of the Paraná and Paraguay Rivers, it significantly influenced the Plata system. Brazil did not, nonetheless, dominate that complex as overwhelmingly as it did the Amazon. Brazil, therefore, came to occupy a powerful geopolitical position with regard to the two major river systems of South America. Although Buenos Aires, the capital of Argentina, became the principal entrepôt of the Plata basin, it had to share this role with Montevideo, Uruguay’s capital, on the northern edge of the river.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Alden, Dauril. Royal Government in Brazil, with Special Reference to the Administration of the Marquis of Lavradio, Viceroy, 1769-1779. Berkeley: University of California Press, 1968. Based on detailed research in primary sources, this book traces the political and diplomatic developments leading to the signing of the Treaty of Madrid together with subsequent modifications.
  • citation-type="booksimple"

    xlink:type="simple">Bethell, Leslie, ed. Colonial Brazil. Cambridge, England: Cambridge University Press, 1986. Compilation of articles by leading specialists on early Brazilian history; places the Treaty of Madrid within its eighteenth century historical context.
  • citation-type="booksimple"

    xlink:type="simple">Boxer, Charles. The Golden Age of Brazil, 1695-1750: Growing Pains of a Colonial Society. Berkeley: University of California Press, 1962. Reviews economic, demographic, and political developments in early eighteenth century Brazil that prompted initiatives for the Treaty of Madrid.
  • citation-type="booksimple"

    xlink:type="simple">Davidson, David Michael. Rivers and Empire: The Madeira Route and the Incorporation of the Brazilian Far West, 1737-1808. Unpublished doctoral dissertation. Yale University, 1970. Focusing on the valley of the Madeira River, a major tributary of the Amazon, this work details Brazilian Portuguese frontier settlement dynamics that required treaty negotiations to recognize occupied territory that in legal theory was within the Spanish domain.
  • citation-type="booksimple"

    xlink:type="simple">Fausto, Boris. A Concise History of Brazil. New York: Cambridge University Press, 1999. This translation of a history of Brazil by a leading Brazilian scholar places the events of the eighteenth century within the wider scope of the country’s development.
  • citation-type="booksimple"

    xlink:type="simple">Maxwell, Kenneth. Pombal: Paradox of the Enlightenment. New York: Cambridge University Press, 1995. Examines the life of the influential Portuguese minister who opposed the Treaty of Madrid; written by a leading scholar of Portuguese history.
  • citation-type="booksimple"

    xlink:type="simple">Scobie, James R. Argentina: A City and a Nation. 2d ed. New York: Oxford University Press, 1971. Standard history of Argentina in English that places the events of the eighteenth century in the larger context of the country’s development.
  • citation-type="booksimple"

    xlink:type="simple">Whigan, Thomas. The Politics of River Trade: Tradition and Development in the Upper Plata, 1780-1870. Albuquerque: University of New Mexico Press, 1991. Analyzes international political and commercial issues in the Plata River system subsequent to the Treaty of Madrid and the Treaty of San Ildefonso.

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