The Primary Result of the 1819 Adams-Onis Treaty

Result Adams-Onis Treaty 1819

Following the War of 1812 there remained but one territory along the eastern seaboard that did not belong to the United States: Florida. Just what is Adams-Onis Treaty of 1819 and how did it relate to Florida and the American west?

For years following the American Revolution the United States attempted to purchase the Spanish territory of Florida. Spanish control of Florida was weak and the native Seminole nation would frequently conduct raids into southern Georgia.

With the acquisition of the Louisiana Purchase in 1803 the United States gained a vast amount of territory from France. This territory now gave the US a direct border with Spain to the south (via Florida) and west (via New Spain provinces).

Conflicts with Spain immediately began over the boundary lines of the new territory. Successive administrations from Jefferson to Madison were unable to reach a diplomatic solution.

During the “Era of Good Feelings” under President James Monroe and against the backdrop of the Panic of 1819 and debates on the Missouri Compromise, Secretary of State John Quincy Adams was finally able to secure a treaty with Spain under the historic Adams-Onis Treaty of 1819.

Under the terms of the Adams-Onis treaty, Spain ceded Florida to the United States and a new boundary line was drawn in the American west. The United States now had an official claim via treaty to the Pacific Ocean.

Importantly, the United States absolved Spain of all financial obligations to American citizens and assumed liability of up to $5 million for damages.

The Adams-Onis treaty of 1819 is seen as a masterstroke of American diplomacy and is considered one of Quincy Adams’ finest moments in a distinguished career. His success helped him win the election of 1824 or “corrupt bargain” as it is sometimes known.

Background of the Florida Territory and Spanish Relations

Spain long held territorial rights over the Florida territory since the very beginning of European colonization of the Americas. Following the French and Indian War, Spain was forced to cede Florida to Great Britain in order to get its prized colony of Cuba back.

The British only ruled for twenty years, but importantly they divided the territory into two provinces: East and West Florida. Spain was an unofficial ally with the colonists in the American Revolution, and in the Treaty of Paris (1783) Britain returned the Floridas to Spain.

As early as the 1790s the United States began negotiations with Spain over purchasing Florida. Spain declined, and instead the two nations signed Pinckney’s Treaty in 1795 to settle a border dispute over Florida.

Territorial disputes once again arose with Spain after the United States purchased the Louisiana territory from France in 1803.

The US argued that the territory of Louisiana consisted by the definition provided by French explorer Rene-Robert de La Salle of the Mississippi River and “all lands that flow to it.” They also demanded that parts of West Florida and Tejas were included in the purchase.1

Spain denied these claims, especially around the Florida and Tejas territories. Successive Democratic-Republican administrations from Jefferson to Madison failed to produce an agreement defining the new boundaries with Spain.

John Quincy Adams Adams-Onis treaty of 1819
US diplomat and Secretary of State John Quincy Adams via LOC

By 1817-1819 pressure was mounting in both nations to strike an agreement. The important War of 1812 had convinced the United States that Florida must be acquired for national security purposes. The British had used the Florida coasts as a base of operations in the war and while out of US hands this area would always remain a threat.1

General Andrew Jackson invaded the Florida territory in 1818 under the guise of protecting American settlers in response to repeated raids into US territory from the Seminole nation.

The ease with which Jackson occupied Spanish forts alarmed Spain as they feared the Americans would simply take the territory by force. These conditions brought the US and Spain to the negotiating table to finally come to an agreement.

The Primary Result of the 1819 Adams-Onis Treaty

The primary result of the Adams-Onis Treaty signed between the United States and Spain in 1819 is that it delineated the boundary of the Louisiana Purchase and transferred possession of Florida from Spain to the US. The treaty is also known as the “Transcontinental Treaty” or the “Florida Purchase,” though the latter is a misnomer.

Secretary of State John Quincy Adams and Spanish envoy to the United States Luis de Onis signed the Adams-Onis treaty on February 22, 1819.

Though the treaty was signed in early 1819, it took the Spanish government over a year to ratify the treaty, finally doing so in October 1820. The treaty went in full effect upon US ratification in February 1821.2

The Adams-Onis Treaty solved many long-standing disputes between the United States and Spain and the agreement was a massive victory for American diplomacy.

Adams-Onis Treaty of 1819 map
Map of the Adams-Onis treaty of 1819 via Wikimedia

The Louisiana border was in desperate need of a resolution. Spain recognized the border in Texas at the Sabine river, while some Americans believed the border was as far south as the Rio Grande.1

Adams craftily drew a new border with Spain to more carefully define territorial boundaries. In a huge victory Adams was able to limit Spain’s northern boundary at the 42nd parallel north, giving the US a claim to the Pacific Ocean.

Adams, however, needed to concede the United States’ claims to Texas in exchange for Florida and other favorable boundaries. The US Senate ratified the Adams-Onis treaty unanimously in just two days primarily in order to avoid popular discontent over the Texas omission.3 

Another section of the treaty absolved Spain from liability for damages claimed by American citizens. These damage claims dated as far back to unlawful seizures during the Quasi-French war and the brief Spanish refusal to allow American trade in New Orleans in 1802.1 Instead, the United States specifically capped the amount of damages it would pay to American citizens at $5 million.

Thus, because the US paid no money to Spain, the claim that the United States purchased Florida is simply inaccurate.

What did the Adams-Onis Treaty Accomplish?

The Adams-Onis Treaty helped to accomplish a long-standing goal of the United States to acquire Florida, as well as properly define the boundary of the Louisiana Purchase. This massive achievement did not come without its tribulations.

Adams and Onis signed the initial treaty in February 1819 though it was subject to ratification from the Spanish government. Ratification did not occur until over a year and a half after the initial agreement in October 1820.

During this period the treaty appeared to be in doubt at several intervals. Onis himself backtracked on the initial treaty, believing that the United States would recognize the independence of the Spanish colonies once the treaty was signed.2

Luis de Onis Adams-Onis treaty
Picture of Luis de Onis via Wikimedia

At this time Spain was dealing with the South and Central American independence movements in their colonies in the Americas. One of the primary Spanish objectives in the negotiations was to ensure that the United States remained neutral over these independence movements. However, the US refused to accept those terms.4

Instead, Spain intentionally delayed ratifying the treaty. The nation hoped to bolster their bargaining position by waiting it out for more favorable conditions. Spain also threw a curveball and stated that the King of Spain had issued land grants in Florida totaling nearly one-third of all public lands right before the treaty signing.2

The ratification delay and Spanish duplicity caused American leaders to consider drastic action. Influential leaders such as Henry Clay and William Crawford called for the immediate occupation of Florida despite the lack of a ratified treaty.

Following the Spanish revolution of 1820, the new government finally agreed to ratify the treaty in October 1820, adding a new clause that annulled the disputed land grants issued by the King.2

President Monroe formally signed the Adams-Onis treaty on February 22, 1821.

The Significance of the Adams-Onis Treaty

The Adams-Onis Treaty of 1819 was a significant achievement in American diplomacy. The treaty tremendously contributed to the territorial expansion of the United States and aided in the nascent calls for “Manifest Destiny,” or the right of the US to extend across the continent.

For the first time the United States was guaranteed a continuous Atlantic seaboard, which was a major boon for security and commerce.

The treaty also limited Spain’s northern territory to the 42nd parallel. giving the United States a claim by treaty to territory along the Pacific coast. The Adams-Onis treaty was the foundation for the eventual acquisition of the Oregon territory.2

Another significant impact of the treaty was that the Sabine river delineated the southwest boundary around Tejas. This boundary did not stop American settlers from pouring into Tejas and eventually sparking the Texas Revolution highlighted by the Battle of the Alamo and Battle of San Jacinto.

What is Adams-Onis Treaty of 1819 Florida chart

The conflict over Tejas and the Mexican-American War could have been avoided had John Quincy Adams not been overruled by President James Monroe in his quest to draw the boundary line at the Rio Grande river.2

Abandoning Texas in the negotiations was one of Adams’ main regrets, though it was necessary in order to secure the other favorable inclusions in the treaty.3

A last major result of the Adams-Onis treaty was the United States’ recognition of independence of the former Spanish colonies in Central and South America. As Onis and Spain feared, this action occurred just a year after the treaty went into effect.

The recognition of independence was a primary motivation behind the monumental Monroe Doctrine that guided US foreign policy for decades into the future.

Overall, the Adams-Onis treaty was a significant achievement for the burgeoning United States.


To learn more about US history, check out this timeline of the history of the United States.


1) Warren, Harris G. “Textbook Writers and the Florida ‘Purchase’ Myth.” The Florida Historical Quarterly, vol. 41, no. 4, Florida Historical Society, 1963, pp. 325–31,

2) Harris, Lester. “The Cession of Florida and John Quincy Adams, Secretary of State, U. S. A.” The Florida Historical Quarterly, vol. 36, no. 3, Florida Historical Society, 1958, pp. 223–38,

3) Price, Grady D. The Southwestern Historical Quarterly, vol. 45, no. 4, Texas State Historical Association, 1942, pp. 387–89,

4) Bisceglia, Louis R. “The Florida Treaty and the Gallatinvives Misunderstanding.” The Florida Historical Quarterly, vol. 48, no. 3, Florida Historical Society, 1970, pp. 247–63,

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