Adams-Onís Treaty Gives the United States Florida Summary

  • Last updated on November 10, 2022

One of the most important treaties in U.S. history, this agreement resolved almost all conflicts between the United States and Spain, gave the United States Florida, settled the boundaries between the Louisiana Territory and Spanish possessions to the west, and signaled the entry of the United States as a world power.

Summary of Event

After the War of 1812, the United States intensified its efforts to resolve long-standing disputes with Spain. Spanish difficulties with the United States had entered a critical new phase during the undeclared U.S. naval war with France that lasted from 1798 to 1800. As an ally of France at that time, Spain had permitted its ships to assist in ransacking U.S. commerce on the high seas and allowed the French to seize U.S. ships in Spanish ports. The United States later demanded compensation from Spain for the loss of these vessels and cargoes. In 1802, the Spanish suspended the right of the United States to deposit and transfer goods at New Orleans, New Orleans which was then under Spanish rule, damaging U.S. commerce in the trans-Appalachian West. Although the Treaty of San Lorenzo of 1795—which was also known as the Pinckney Treaty Pinckney’s Treaty (1795)[Pinckneys Treaty] —between the United States and Spain had guaranteed U.S. deposit rights and prohibited privateering by either nation upon the other, the Spanish balked at paying compensation for its transgressions, leaving the dispute unresolved in 1805. Adams-Onís Treaty (1819)[Adams Onis Treaty (1819)] Spain;and United States[United States] Florida;and Adams-Onís Treaty[Adams Onís Treaty] Louisiana Territory;Adams-Onís Treaty Foreign policy, U.S.;Adams-Onís Treaty Adams, John Quincy [p]Adams, John Quincy;and Adams-Onís Treaty[Adams Onis Treaty] Onís, Luis de Florida;and Adams-Onís Treaty[Adams Onis Treaty] [kw]Adams-Onís Treaty Gives the United States Florida (Feb. 22, 1819) [kw]Onís Treaty Gives the United States Florida, Adams- (Feb. 22, 1819) [kw]Treaty Gives the United States Florida, Adams-Onís (Feb. 22, 1819) [kw]Gives the United States Florida, Adams-Onís Treaty (Feb. 22, 1819) [kw]United States Florida, Adams-Onís Treaty Gives the (Feb. 22, 1819) [kw]Florida, Adams-Onís Treaty Gives the United States (Feb. 22, 1819) Adams-Onís Treaty (1819)[Adams Onis Treaty (1819)] Spain;and United States[United States] Florida;and Adams-Onís Treaty[Adams Onís Treaty] Louisiana Territory;Adams-Onís Treaty Foreign policy, U.S.;Adams-Onís Treaty Adams, John Quincy [p]Adams, John Quincy;and Adams-Onís Treaty[Adams Onis Treaty] Onís, Luis de Florida;and Adams-Onís Treaty[Adams Onis Treaty] Transcontinental Treaty(1819); [g]United States;Feb. 22, 1819: Adams-Onís Treaty Gives the United States Florida[0990] [g]Spain;Feb. 22, 1819: Adams-Onís Treaty Gives the United States Florida[0990] [c]Diplomacy and international relations;Feb. 22, 1819: Adams-Onís Treaty Gives the United States Florida[0990] [c]Expansion and land acquisition;Feb. 22, 1819:Adams-Onís Treaty Gives the United States Florida[0990] Madison, James [p]Madison, James;and Adams-Onís Treaty[Adams Onis Treaty] Monroe, James [p]Monroe, James;and Adams-Onís Treaty[Adams Onis Treaty] Ferdinand VII Jackson, Andrew [p]Jackson, Andrew;in Florida[Florida]

The U.S. purchase of Louisiana Louisiana Purchase;and Spain[Spain] from France in 1803 complicated Spanish-American relations. The French had obtained the territory from Spain in the Treaty of San Ildefonso San Ildefonso, Treaty of (1800) of 1800. By that agreement, France had pledged not to transfer Louisiana to another power without first offering to restore the territory to Spain. The Spanish thus considered the U.S. purchase of the territory to be illegal and continued to demand its return until 1818. Meanwhile, the United States quickly defined Louisiana’s boundaries, part of which ran along two adjacent Spanish provinces, Texas and West Florida. U.S. claims to the latter territory were dubious at best, and Spanish rights to western and central Texas Texas were solidly founded upon the chain of Spanish forts and missions that had established there before 1800. East Texas, however, was largely unsettled and would become the crux of the dispute after the War of 1812.

U.S. interest in Spanish territory also extended to areas to which the United States could make no plausible legal claims. East Florida was one such area, and the United States negotiated continuously for its purchase, beginning in the 1790’s. U.S. government leaders believed that possession of Florida would give the United States command of the Gulf of Mexico and secure from foreign interference the trade that passed through the Mississippi River. After 1808, U.S. prospects for acquiring both West and East Florida improved greatly: Napoleon had invaded Spain, diverting most of that nation’s resources to a life-or-death struggle against France.

In the summer of 1810, the United States colluded in the successful rebellion of settlers in the Baton Rouge region of West Florida. Later during that same year, the area was legally annexed to the United States up to the Pearl River and later became part of the state of Louisiana. After the United States went to war with Great Britain in 1812, the U.S. government came under domestic pressure to use the opportunity to expand at Spain’s expense. In the spring of 1813, Congress authorized the occupation of Mobile, the principal Spanish port in the section of West Florida between the Pearl and Perdido Rivers. The Spanish responded to U.S. aggression by allowing the British to use Pensacola as a base, and by assisting the Creek Creeks Indians in their 1813-1814 war against the United States. The War of 1812 War of 1812 (1812-1814);and Florida[Florida] thus dramatically illustrated U.S. vulnerability: In the hands of Spain, Florida had become a yawning gap in the coastal defenses of the United States—a highway through which the interior of the country could be penetrated easily.

After the United States concluded the Treaty of Ghent with Great Britain in early 1815, the acquisition of East Florida became the prime goal of U.S. foreign policy. Spain recognized that it had only two choices to avoid a shameful abandonment of the region: to gain the support of a European ally, or to attain a semblance of honor in the affair by winning from the United States favorable territorial concessions west of the Mississippi. At first, the Spanish were successful in securing the support of the British, who warned the United States against further encroachments on their neighbors.

Bolstered by Britain’s encouragement, Luis de Onís, Spain’s minister to the United States, successfully sparred with his counterpart, Secretary of State James Monroe Monroe, James [p]Monroe, James;and Adams-Onís Treaty[Adams Onis Treaty] , throughout 1815 and 1816. The Spaniard demanded the return of Louisiana and West Florida to Spain and protested against American supplying of revolutionaries fighting against Spain in Spain’s Central and South American colonies and American support of the privateers operating out of Baltimore that preyed on Spanish shipping. Soon, Spain had developed its own list of financial claims against the United States and was demanding compensation. President James Madison Madison, James [p]Madison, James;and Adams-Onís Treaty[Adams Onis Treaty] declined to intensify the diplomatic struggle, because delay only aided the United States, which was growing stronger, as Spain was growing weaker.

The inauguration of former secretary of state James Monroe Monroe, James [p]Monroe, James;and Adams-Onís Treaty[Adams Onis Treaty] as president in March, 1817, placed the negotiations in impatient, decisive hands. Monroe was determined to push the Spanish to an agreement and appointed a secretary of state, John Quincy Adams, who shared his views. In the fall of 1817, the U.S. cabinet decided to adopt a new attitude toward Spain, a decision that resulted in the dispatch of an army under the command of Major General Andrew Jackson Jackson, Andrew [p]Jackson, Andrew;in Florida[Florida] into Florida—ostensibly to pursue Seminoles Seminoles;and Andrew Jackson[Jackson] who were raiding in retaliation for the destruction of one of their villages.

Jackson’s orders from Washington were ambiguous: He was authorized to enter Florida to punish the Seminoles but was forbidden to attack them if they sheltered under a Spanish fort. At the same time, he was also enjoined to adopt the measures necessary to end the conflict. After Jackson was actually in Florida, he discovered evidence of Spanish aid to the Seminoles. Relying on the discretion allotted to him, he judged that only the capture of Spanish forts would end the conflict. Jackson accordingly adopted these “necessary measures” by seizing St. Marks and Pensacola, effectively wresting Florida from Spain.

Although the U.S. administration would later deny having intended that Jackson Jackson, Andrew [p]Jackson, Andrew;in Florida[Florida] should take such extreme action, Adams used the military pressure to force the Spanish to retreat from their extreme negotiating positions. International conditions also encouraged Spain to accommodate U.S. demands. By early 1818, Great Britain had made it clear that it would not risk war with the United States by seeking to enforce mediation of Spanish-American disputes. European commitments and dangers had caused the British to reconsider their support for Spain and to seek détente with the United States. In the summer, Great Britain agreed to negotiate with the United States over all outstanding issues. These talks resulted in the Convention of 1818. The British-American rapprochement thus ended Spanish pretensions to power.

Negotiations between the United States and Spain resumed in the fall of 1818, after the United States had agreed to restore the forts to the Spanish. Near the end of the year, the two nations agreed upon a western boundary that went up the Sabine River from its mouth and continued north to the Red River Red River (Arkansas) , zigzagged westward along the Red and Arkansas Rivers, followed the crest of the Rocky Mountains to the forty-second parallel, and then turned westward to the Pacific Ocean.

On February 22, 1819, Adams and Onís signed the treaty that bears their names. It embodied the compromise western boundary and resolved nearly all the disputes between their two nations. The Spanish retained Texas Texas but gave up claims to the Oregon Country. Spain ceded all its territory east of the Mississippi to the United States. Both nations renounced their claims for damages, although the United States agreed to assume the claims of its citizens against Spain up to a maximum of five million dollars.

Adams successfully avoided guaranteeing that the United States would not recognize the Latin American nations claiming independence from Spain. At first, King Ferdinand Ferdinand VII VII of Spain refused to ratify the treaty because the United States had failed to provide such guarantees. However, a January, 1820, revolution in Spain brought to power a liberal regime whose leaders were inclined to accommodate the United States. France and Russia, who feared that the Spanish-American quarrel threatened world peace, pressured the new Spanish government to settle. Spain finally ratified the treaty in October, 1820, and the Adams-Onís Treaty (also known as the Transcontinental Treaty) became effective on February 22, 1821.


The Adams-Onís Treaty was crucial to determining the course of North American history. It signified the decay of Spanish power in the New World and provided conclusive evidence of British acquiescence in limited United States expansion. The acquisition of Florida strengthened the United States materially and enhanced its national security by closing a gap in its coastal defenses. Spain’s recognition of U.S. rights in Oregon signaled the beginning of the role of the United States as a global power. Resolving problems with Spain largely freed the United States from European entanglements for several decades.

The treaty also played a decisive role in modern Seminole Seminoles;and Adams-Onís Treaty[Adams Onis Treaty] history. By replacing stagnant Spanish rule with that of a demographically and economically expanding United States, the treaty ensured that the Seminoles could not long remain in possession of their lands. Their removal westward almost inevitably followed during the 1830’s.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Bemis, Samuel F. John Quincy Adams and the Foundations of American Foreign Policy. New York: Alfred A. Knopf, 1949. Detailed examination of Adams’s role in the treaty negotiations, strongly emphasizing the continentalism in his thinking.
  • citation-type="booksimple"

    xlink:type="simple">Brooks, Philip C. Diplomacy and the Borderlands: The Adams-Onís Treaty of 1819. Berkeley: University of California Press, 1939. This highly detailed account of the negotiations unfortunately emphasizes legal aspects of the treaty so strongly that the book obscures the role of power in determining the treaty’s final shape.
  • citation-type="booksimple"

    xlink:type="simple">Cox, Isaac J. The West Florida Controversy, 1798-1813: A Study in American Diplomacy. 1918. Reprint. Gloucester, Mass.: Peter Smith, 1967. Although inadequate in several respects, this study provides an excellent summary of the development of Spanish-American disputes before 1815.
  • citation-type="booksimple"

    xlink:type="simple">Griffin, Charles C. The United States and the Disruption of the Spanish Empire, 1810-1822. New York: Columbia University Press, 1937. Stresses the domestic and international context of the negotiations. Analysis of U.S. public opinion illuminates United States decision making.
  • citation-type="booksimple"

    xlink:type="simple">Missall, John, and Mary Lou Missall. The Seminole Wars: America’s Longest Indian Conflict. Gainesville: University Press of Florida, 2004. Study of the three Seminole wars that examines their causes and significance in American history, including the U.S. acquisition of Florida from Spain.
  • citation-type="booksimple"

    xlink:type="simple">Remini, Robert V. Andrew Jackson. 3 vols. Baltimore: Johns Hopkins University Press, 1998. The first volume of this major biography covers Jackson’s role in territorial expansion, including his pivotal role in the U.S. acquisition of Florida.
  • citation-type="booksimple"

    xlink:type="simple">Weeks, William E. John Quincy Adams and American Global Empire. Lexington: University Press of Kentucky, 1992. A balanced account of the treaty negotiations, which includes the role of U.S. expansionism and aggression. Unlike some earlier historians, Weeks does not regard the Florida cession as the almost inevitable result of Spanish decay.

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