Luis de Onís y González-Vara (4 June 1762 – 17 May 1827) was a career Spanish diplomat who served as Spanish
Envoy
Envoy or Envoys may refer to:
Diplomacy
* Diplomacy, in general
* Envoy (title)
* Special envoy, a type of Diplomatic rank#Special envoy, diplomatic rank
Brands
*Airspeed Envoy, a 1930s British light transport aircraft
*Envoy (automobile), an au ...
to the United States from 1809 to 1819,
and is remembered for negotiating the cession of Florida to the US in the
Adams–Onís Treaty with
United States Secretary of State
The United States secretary of state (SecState) is a member of the executive branch of the federal government of the United States and the head of the U.S. Department of State.
The secretary of state serves as the principal advisor to the ...
John Quincy Adams
John Quincy Adams (; July 11, 1767 – February 23, 1848) was the sixth president of the United States, serving from 1825 to 1829. He previously served as the eighth United States secretary of state from 1817 to 1825. During his long diploma ...
, in 1819.
Biography
Family and early life
Luis de Onís was born in
Cantalapiedra,
Salamanca
Salamanca () is a Municipality of Spain, municipality and city in Spain, capital of the Province of Salamanca, province of the same name, located in the autonomous community of Castile and León. It is located in the Campo Charro comarca, in the ...
on 30 June 1762.
He was the son of Joaquin de Onís, a landowner who was probably of noble
Asturian origin.
Luis received a classical education at home; he began the study of Greek and Latin when he was 8, and by 16, he had concluded his studies in the humanities and law at the
University of Salamanca
The University of Salamanca () is a public university, public research university in Salamanca, Spain. Founded in 1218 by Alfonso IX of León, King Alfonso IX, it is the oldest university in the Hispanic world and the fourth oldest in the ...
.
Early work as an ambassador
In 1780, Onís joined his uncle, José de Onís,
ambassador
An ambassador is an official envoy, especially a high-ranking diplomat who represents a state and is usually accredited to another sovereign state or to an international organization as the resident representative of their own government or so ...
of Spain to the
Electorate of Saxony
The Electorate of Saxony, also known as Electoral Saxony ( or ), was a territory of the Holy Roman Empire from 1356 to 1806 initially centred on Wittenberg that came to include areas around the cities of Dresden, Leipzig and Chemnitz. It was a ...
in
Dresden
Dresden (; ; Upper Saxon German, Upper Saxon: ''Dräsdn''; , ) is the capital city of the States of Germany, German state of Saxony and its second most populous city after Leipzig. It is the List of cities in Germany by population, 12th most p ...
, Germany, who was known as one of the most accomplished men in politics, science, and
belles lettres of the time. Luis joined the legation as his personal secretary and assumed duties as a trade commissioner. In the course of his work, he visited the royal courts of Berlin and Vienna as well as the courts of the other capital cities in Central Europe.
In 1786, when he was 24 years old, Onís was sent on an important mission by the Spanish government, which knew that
Saxony
Saxony, officially the Free State of Saxony, is a landlocked state of Germany, bordering the states of Brandenburg, Saxony-Anhalt, Thuringia, and Bavaria, as well as the countries of Poland and the Czech Republic. Its capital is Dresden, and ...
had the most highly developed mining industry in Europe and desired to acquire experienced miners to send to its American colonies. He went to study at the
School of Mines in
Freiberg, a town dominated by the mining and smelting industries, and enrolled in a course taught by the Prussian mineralogist, Professor
Abraham Gottlob Werner. Becoming acquainted with operations in the mines, Onís learned of the existence of a surplus of miners looking for employment. Subsequently, the
Count of Floridablanca decided to entrust the mission to the young man. He met with a diplomatic minister of Saxony, who was prepared to reject his request, but he was so impressed by the young man's knowledge of the pertinent facts and the force of his arguments that he agreed to his request and allowed him to choose thirty-six miners, including six managers, to send to Spain. In recognition of Onis's success, the Count proposed to appoint him as a minister to the United States, a promotion that he could not then accept.
In 1792, Onís was decorated with the Cross of
Charles III of Spain (''Cruz de Carlos III'').
In 1798, he returned to Spain, where he was appointed to a position in the office of the First Secretary of State (''Primer Secretaría de Estado'') in
Madrid
Madrid ( ; ) is the capital and List of largest cities in Spain, most populous municipality of Spain. It has almost 3.5 million inhabitants and a Madrid metropolitan area, metropolitan area population of approximately 7 million. It i ...
, being responsible for conducting negotiations with France. In April 1802, he took an active part in the negotiations for and the conclusion of the
Treaty of Amiens and, in October, he was granted the customary perks of a "secretary to the King" (''Secretario del rey''), including a house and an expense account.
Following
Napoleon Bonaparte
Napoleon Bonaparte (born Napoleone di Buonaparte; 15 August 1769 – 5 May 1821), later known by his regnal name Napoleon I, was a French general and statesman who rose to prominence during the French Revolution and led Military career ...
's invasion of Spain in 1808 and with the impending abdication of
Ferdinand VII, the remnant of the royal government moved to Seville,
where Onís continued in his capacity as longest-serving senior officer of the Ministry.
He soon received a proposal to lead a
diplomatic mission
A diplomatic mission or foreign mission is a group of people from a state or organization present in another state to represent the sending state or organization officially in the receiving or host state. In practice, the phrase usually denotes ...
to St. Petersburg, and then a designation to Sweden, neither of which came to pass. Finally, the Junta Central (the anti-French Spanish Government fighting Napoleon's brother,
Joseph Bonaparte, now king of Spain as José I), decided to send him to the United States.
Ambassador to the United States
On 29 June 1809,
Onís was appointed minister plenipotentiary (with full powers to take independent action) to the United States, his letter of appointment instructing him to embark as soon as possible for New York.
His assignment was to ensure peace between the two nations and win formal recognition of
Fernando VII as the legitimate ruler of Spain. He was to negotiate all points in dispute within certain defined limits; to encourage the loyalty of Spain's colonies in the
New World
The term "New World" is used to describe the majority of lands of Earth's Western Hemisphere, particularly the Americas, and sometimes Oceania."America." ''The Oxford Companion to the English Language'' (). McArthur, Tom, ed., 1992. New York: ...
; to buy supplies, armaments, and ships for Spain to use in its war against the French; and to counter
Bonapartist propaganda in the US.
He was to pursue these objectives despite the refusal of President
James Madison
James Madison (June 28, 1836) was an American statesman, diplomat, and Founding Fathers of the United States, Founding Father who served as the fourth president of the United States from 1809 to 1817. Madison was popularly acclaimed as the ...
to recognize him while the
Peninsular War
The Peninsular War (1808–1814) was fought in the Iberian Peninsula by Kingdom of Portugal, Portugal, Spain and the United Kingdom of Great Britain and Ireland, United Kingdom against the invading and occupying forces of the First French ...
still raged in Europe.
Arriving at the port of New York on 4 October 1809 aboard the Spanish frigate ''Cornelia'', after a rough passage of 44 days, Onís requested an audience to present his credentials to President Madison but was promptly informed that the US government could not receive or recognize any minister from the provisional governments of Spain as long as the crown was in dispute and that until that question was resolved, the United States would remain neutral.
Consequently, no member of the
Cabinet would recognize him or enter into any official communication with him.
The United States did not officially recognize Onís as ambassador until December 1815, all the while asserting that political considerations obliged it to remain neutral until the conclusion of the war in Spain
despite assurances of support for the cause of Spanish independence by Madison.
Soon after his arrival in the United States, Onís took up residence in
Philadelphia
Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
, where he used the officially recognized consular office to run a shadow legation
and worked tirelessly against attempts by the United States to penetrate into Florida,
as well as its covert support for French agents moving to infiltrate the Spanish provinces.
He paid special attention to the activities of Spanish and Latin American revolutionary agents, who sought to exploit the sympathy that American citizens felt for Spain's rebelling colonies in South America.
Secretary of State
James Monroe
James Monroe ( ; April 28, 1758July 4, 1831) was an American Founding Father of the United States, Founding Father who served as the fifth president of the United States from 1817 to 1825. He was the last Founding Father to serve as presiden ...
rejected his written protests but clandestinely lent his support to insurgent movements led by filibusterers
and irregular American forces.
The occupation of West Florida in 1810 was the culmination of a prolonged series of events over the course of several years,
as a consequence of the indeterminacy of the border between
Florida
Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
and
Louisiana Purchase
The Louisiana Purchase () was the acquisition of the Louisiana (New France), territory of Louisiana by the United States from the French First Republic in 1803. This consisted of most of the land in the Mississippi River#Watershed, Mississipp ...
when
France
France, officially the French Republic, is a country located primarily in Western Europe. Overseas France, Its overseas regions and territories include French Guiana in South America, Saint Pierre and Miquelon in the Atlantic Ocean#North Atlan ...
ceded it to Spain in 1763. At the start of the
War of 1812
The War of 1812 was fought by the United States and its allies against the United Kingdom of Great Britain and Ireland, United Kingdom and its allies in North America. It began when the United States United States declaration of war on the Uni ...
between the United States and
Great Britain
Great Britain is an island in the North Atlantic Ocean off the north-west coast of continental Europe, consisting of the countries England, Scotland, and Wales. With an area of , it is the largest of the British Isles, the List of European ...
, the danger of invasion of
East Florida, a territory that had never been in dispute, escalated and was a constant subject of concern in Onís's correspondence with Monroe. The US government finally officially recognized Onís as Ambassador of Spain, and he presented his credentials on December 20, 1815, five years after his arrival in New York.
Thereafter, he continued asserting the Spanish arguments with his customary vigor.
Monroe, meanwhile, sent an ambassador to Madrid, John Erving,
who was snubbed by the Spanish Secretary of State,
Pedro Cevallos, and had to wait several months for formal recognition of Onís's ambassadorship to the United States. Cevallos opposed making any significant concessions to secure a treaty and endeavored to buy more time for Spain with the mere appearance of negotiations. Cevallos transferred consultations from Madrid to Washington and ensured further delays by sending Onís the necessary powers but no instructions to proceed.
Resisting American pressure to begin negotiations in earnest, Onís tried to delay official recognition by Madrid of the US embassy through various subterfuges, such as maneuvering for the replacement of Cevallos, which occurred on 30 October 1816.
During his years in the United States, Onís published several pamphlets critical of its government under the pseudonym "Verus" (Latin: "True").
He advised the Viceroy of
New Spain
New Spain, officially the Viceroyalty of New Spain ( ; Nahuatl: ''Yankwik Kaxtillan Birreiyotl''), originally the Kingdom of New Spain, was an integral territorial entity of the Spanish Empire, established by Habsburg Spain. It was one of several ...
(Mexico),
Francisco Javier Venegas, and the Governor of Cuba, the
Marqués de Someruelos, of the expansionist ambitions of the growing young nation.
During the
Mexican War of Independence
The Mexican War of Independence (, 16 September 1810 – 27 September 1821) was an armed conflict and political process resulting in Mexico's independence from the Spanish Empire. It was not a single, coherent event, but local and regional ...
, he maintained a network of spies
to prevent contact between the rebels and potential allies in the United States. The network was particularly active in the fight against the so-called "insurgent corsairs," many of them
French privateers, who placed themselves at the service of the nascent republics of Spanish America.
Adams–Onís treaty

The Adams–Onís treaty was signed on 22 February 1819
after two years of difficult negotiations and the intervention of the French ambassador
Hyde de Neuville, who defended the Spanish position against the radicalism of
Henry Clay
Henry Clay (April 12, 1777June 29, 1852) was an American lawyer and statesman who represented Kentucky in both the United States Senate, U.S. Senate and United States House of Representatives, House of Representatives. He was the seventh Spea ...
in the United States Congress, and General
Andrew Jackson
Andrew Jackson (March 15, 1767 – June 8, 1845) was the seventh president of the United States from 1829 to 1837. Before Presidency of Andrew Jackson, his presidency, he rose to fame as a general in the U.S. Army and served in both houses ...
, who was notoriously hostile to the Spanish presence in East Florida.
Ratification of the treaty had been postponed for two years since Spain wanted to use it as an incentive to keep the United States from lending diplomatic support to the revolutionaries in South America. As soon as the treaty was signed, the US Senate ratified it unanimously; but because of Spain's stalling, a new ratification was necessary and this time there were objections. Clay and other western spokesmen demanded that Spain also give up Texas, but that proposal was defeated by the Senate, which ratified the treaty a second time on 19 February 1821, following ratification by Spain on 24 October 1820. Ratifications were exchanged three days later and the treaty was proclaimed on 22 February 1821, two years after its signing.
The treaty consisted of 16 articles,
half of which settled issues that had been in dispute since 1783, ceding all the lands of the
Spanish Crown
The monarchy of Spain or Spanish monarchy () is the constitutional form of government of Spain. It consists of a Hereditary monarchy, hereditary monarch who reigns as the head of state, being the highest office of the country.
The Spanish ...
located east of the Mississippi, known as
the Floridas, to the United States. Settling the most serious point of contention, determining the borders to the west and northwest of the
Mississippi
Mississippi ( ) is a U.S. state, state in the Southeastern United States, Southeastern and Deep South regions of the United States. It borders Tennessee to the north, Alabama to the east, the Gulf of Mexico to the south, Louisiana to the s ...
, was delayed until the last moment,
as Onís aimed at all costs to keep Texas, New Mexico and California under the dominion of Spain.
The signing of the treaty received a surprisingly favorable response from the public
and the United States Senate. Onís returned to Europe, convinced that the alternative to signing the treaty would have been the loss of all Spanish territories as far west as the boundaries of the Rio Grande
and parts of the interior provinces (''
Provincias Internas'') of New Spain.
The Adams–Onís Treaty closed the first era of United States expansion by providing for the cession of East Florida; the abandonment of the controversy over West Florida (a portion of which had been seized by the United States); and the delineating of a boundary with the Spanish province of Mexico that clearly made
Spanish Texas a part of Mexico, thus ending much of the vagueness in the boundaries of the Louisiana Purchase.
Spain also ceded, to the US, its claims to the
Oregon Country
Oregon Country was a large region of the Pacific Northwest of North America that was subject to a long Oregon boundary dispute, dispute between the United Kingdom and the United States in the early 19th century. The area, which had been demarcat ...
. For Spain, it meant that it kept Texas and retained a buffer zone between its Californian and New Mexican possessions and the territories of the United States.
In 1820 Onís published a 152-page memoir on the diplomatic negotiation. It was translated from Spanish to English by US diplomatic commission secretary,
Tobias Watkins, and republished in 1821 in the US.
Honors and last years
In 1818, the
Spanish Cortes conferred on Onís the title of ''Regidor perpetuo de Salamanca'' (Perpetual alderman of Salamanca), a title that passed to his descendants in the male line. In mid-1819, Onís was awarded the ''Gran Cruz Americana'' (American Grand Cross) and the honors of ''Consejero de Estado'' (Councilor of State) and was appointed minister to
St. Petersburg. The revolution of 1820, however,
prevented his assuming this office. The new constitutional government revoked the appointment and instead assigned him to the embassy in
Naples
Naples ( ; ; ) is the Regions of Italy, regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 908,082 within the city's administrative limits as of 2025, while its Metropolitan City of N ...
.
The same year, he published a work in two volumes, entitled ''Memoria sobre las Negociaciones entre España y los Estados Unidos de América'' (Memoir Upon the Negotiations between Spain and the United States of America),
a memoir of his role in the negotiations leading to the Treaty of 1819. His last diplomatic mission sent him to
London
London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
in February 1821, where he participated in diplomatic consultations for the recognition of
Hispanic America
Hispanic America ( or ), historically known as Spanish America () or Castile (historical region), Castilian America (), is the Spanish-speaking countries and territories of the Americas. In all of these countries, Spanish language, Spanish is th ...
n countries by the United States and managed to prevent the European powers from following the US example. In November 1822, Onís returned to Madrid,
where he died on 17 May 1827,
after an illness of four days.
Personal life
Luis married Federika Christina von Mercklein in
Dresden
Dresden (; ; Upper Saxon German, Upper Saxon: ''Dräsdn''; , ) is the capital city of the States of Germany, German state of Saxony and its second most populous city after Leipzig. It is the List of cities in Germany by population, 12th most p ...
on 9 August 1788. They had three children:
Mauricio, Narciss, and Clementina.
References
Further reading
* Brooks, Philip Coolidge. ''Diplomacy and the borderlands: the Adams-Onís treaty of 1819'' (U of California Press, 1939).
* Hawkins, Timothy. ''A Great Fear: Luís de Onís and the Shadow War against Napoleon in Spanish America, 1808–1812'' (U of Alabama Press, 2019).
{{DEFAULTSORT:Onis, Luis de
1762 births
1827 deaths
People from the Province of Salamanca
University of Salamanca alumni
Ambassadors of Spain to the United States
Ambassadors of Spain to the United Kingdom