Treaty ceding Spanish Florida to the U.S. (1819)
The Adams–Onís Treaty () of 1819, also known as the Transcontinental Treaty, the Spanish Cession, the Florida Purchase Treaty, or the Florida Treaty, was a treaty between the United States and Spain in 1819 that ceded Florida to the U.S. and defined the boundary between the U.S. and Mexico (New Spain). It settled a standing border dispute between the two countries and was considered a triumph of American diplomacy. It came during the successful Spanish American wars of independence against Spain.
Florida had become a burden to Spain, which could not afford to send settlers or staff garrisons, so Madrid decided to cede the territory to the United States in exchange for settling the boundary dispute along the Sabine River in Spanish Texas. The treaty established the boundary of U.S. territory and claims through the Rocky Mountains and west to the Pacific Ocean, in exchange for Washington paying residents' claims against the Spanish government up to a total of $5 million Spanish dollars (purchasing power ) and relinquishing the U.S. claims on parts of Spanish Texas west of the Sabine River and other Spanish areas, under the terms of the Louisiana Purchase.
The treaty remained in full effect for only 183 days: from February 22, 1821, to August 24, 1821, when Spanish military officials signed the Treaty of Córdoba acknowledging the independence of Mexico; Spain repudiated that treaty, but Mexico effectively took control of Spain's former colony. The Treaty of Limits between Mexico and the United States, signed in 1828 and effective in 1832, recognized the border defined by the Adams–Onís Treaty as the boundary between the two nations.
History.
 
The Adams–Onís Treaty was negotiated by John Quincy Adams, the Secretary of State under U.S. President James Monroe, and the Spanish minister plenipotentiary (diplomatic envoy) Luis de Onís y González-Vara, during the reign of King Ferdinand VII.
Florida.
Spain had long rejected repeated American efforts to purchase Florida. But by 1818, Spain was facing a troubling colonial situation in which the cession of Florida made sense. Spain had been exhausted by the Peninsular War (1807–1814) against Napoleon in Europe and needed to rebuild its credibility and presence in its colonies. Revolutionaries in Central America and South America had been waging wars of independence since 1810. Spain was unwilling to invest further in Florida, encroached on by American settlers, and it worried about the border between New Spain (a large area including today's Mexico, Central America, and much of the current U.S. western states) and the United States. With minor military presence in Florida, Spain was not able to restrain the Seminole warriors who routinely crossed the border and raided American villages and farms, as well as protected southern slave refugees from slave owners and traders of the southern United States.
The United States from 1810 to 1813 annexed and then invaded most of West Florida (already independent as the Republic of West Florida west of the Pearl River) up to the Perdido River (modern border river between the states of Alabama and Florida), claiming that the Louisiana Purchase covered West Florida also. General James Wilkinson invaded and occupied Mobile during the War of 1812 and the Spanish never returned to West Florida west of the Perdido River.
The State of Muskogee (1799–1803) demonstrated Spain's inability to control the interior of East Florida, at least "de facto"; the Spanish presence had been reduced to the capital (San Agustín) and other coastal cities, while the interior belonged to the Seminole nation.
While fighting escaped African-American slaves, outlaws, and Native Americans in U.S.-controlled Georgia during the First Seminole War, American General Andrew Jackson had pursued them into Spanish Florida. He built Fort Scott, at the southern border of Georgia (i.e., the U.S.), and used it to destroy the Negro Fort in northwest Florida, whose existence was perceived as an intolerably disruptive risk by Georgia plantation owners.
To stop the Seminole based in East Florida from raiding Georgia settlements and offering havens for runaway slaves, the U.S. Army led increasingly frequent incursions into Spanish territory. This included the 1817–1818 campaign by Andrew Jackson that became known as the First Seminole War, after which the U.S. effectively seized control of Florida; albeit for purposes of lawful government and administration in Georgia and not for the outright annexation of territory for the U.S. Adams said the U.S. had to take control because Florida (along the border of Georgia and Alabama Territory) had become "a derelict open to the occupancy of every enemy, civilized or savage, of the United States, and serving no other earthly purpose than as a post of annoyance to them". Spain asked for British intervention, but London declined to assist Spain in the negotiations. Some of President Monroe's cabinet demanded Jackson's immediate dismissal for invading Florida, but Adams realized that his success had given the U.S. a favorable diplomatic position. Adams was able to negotiate very favorable terms.
Louisiana.
In 1521, the Spanish Empire created the "Virreinato de Nueva España" (Viceroyalty of New Spain) to govern its conquests in the Caribbean, North America, and later the Pacific Ocean. In 1682, La Salle claimed Louisiana for France. For the Spanish Empire, this was an intrusion into the northeastern frontier of New Spain. In 1691, Spain created the Province of Tejas in an attempt to inhibit French settlement west of the Mississippi River. Fearing the loss of his American territories in the Seven Years' War, King Louis XV of France ceded Louisiana to King Charles III of Spain with the secret Treaty of Fontainebleau in 1762. The Treaty of Paris of 1763 split Louisiana with the portion east of the Mississippi River (except for Île d'Orléans) becoming a part of British North America and the portion west of the river becoming the District of Louisiana within New Spain. This eliminated the French threat, and the Spanish provinces of Luisiana, Tejas, and Santa Fe de Nuevo México coexisted with only loosely defined borders. In 1800, French First Consul Napoleon Bonaparte forced King Charles IV of Spain to cede Louisiana to France with the secret Third Treaty of San Ildefonso. Spain continued to administer Louisiana until 1802 when Spain publicly transferred the district to France. The following year, Napoleon sold the territory to the United States to raise money for his military campaigns.
The United States and the Spanish Empire disagreed over the territorial boundaries of the Louisiana Purchase of 1803. The United States maintained the claim of France that Louisiana included the Mississippi River and "all lands whose waters flow to it". To the west of New Orleans, the United States assumed the French claim to all land east and north of either the Sabine River or the Rio Grande. Spain maintained that all land west of the Calcasieu River and south of the Arkansas River belonged to Tejas and Santa Fe de Nuevo México.
Oregon Country.
The British government claimed the region west of the Continental Divide between the undefined borders of Alta California and Russian Alaska on the basis of (1) the third voyage of James Cook in 1778, (2) the Vancouver Expedition in 1791–1795, (3) the solo journey of Alexander Mackenzie to the North Bentinck Arm in 1792–1793, and (4) the exploration of David Thompson in 1807–1812. The Third Nootka Convention of 1794 stipulated that both the British and Spanish would abandon any settlements they had in the Nootka Sound.
The United States claimed essentially the same region on the basis of (1) the voyage of Robert Gray up the Columbia River in 1792, (2) the United States Lewis and Clark Expedition of 1804–1806, and (3) the establishment of Fort Astoria on the Columbia River in 1811. On 20 October 1818, the Anglo-American Convention of 1818 was signed setting the border between British North America and the United States east of the Continental Divide along the 49th parallel north and calling for joint Anglo-American occupancy west of the Great Divide. The Anglo-American Convention ignored the Nootka Convention of 1794 which gave Spain joint rights in the region. The convention also ignored Russian settlements in the region. The U.S. government referred to this region as the Oregon Country, while the British government referred to the region as the Columbia District.
Russian America.
On 16 July 1741, the crew of the Imperial Russian Navy ship "" ("Святой Пётр"), captained by Vitus Bering, sighted Mount Saint Elias, the fourth-highest summit in North America. While dispatched on the Russian Great Northern Expedition, they became the first Europeans to land in northwestern North America. The Russian fur trade soon followed the discovery. By 1812, the Russian Empire claimed Alaska and the Pacific Coast of North America as far south as the Russian settlement of Fortress Ross, only northwest of the Spain's Presidio Real de San Francisco.
New Spain.
The Spanish Empire claimed all lands west of the Continental Divide throughout the Americas. Between 1774 and 1779, King Charles III of Spain ordered three naval expeditions north along the Pacific Coast to assert Spain's territorial claims. In July 1774, Juan José Pérez Hernández reached latitude 54°40′ north off the northwestern tip of Langara Island before being forced to turn south. On 15 August 1775, Juan Francisco de la Bodega y Quadra reached the latitude 59°0′ before returning south. On 23 July 1779, Ignacio de Arteaga y Bazán and Bodega y Quadra reached Puerto de Santiago on Isla de la Magdalena (now Port Etches on Hinchinbrook Island) where they held a formal possession ceremony commemorating Saint James, the patron saint of Spain. This marked the northernmost Spanish exploration in the Pacific Ocean.
Between 1788 and 1793, Spain launched several more expeditions north of Alta California. On 24 June 1789, Esteban José Martínez Fernández y Martínez de la Sierra established the Spanish colony of Santa Cruz de Nuca on the northwest coast of Vancouver Island. Asserting Spain's claim of exclusive sovereignty and navigation rights, Martínez seized several ships in Nootka Sound provoking the Nootka Crisis with Great Britain. In negotiations to resolve the crisis, Spain claimed that its Nootka Territory extended north from Alta California to the 61st parallel north and from the Continental Divide west to the 147th meridian west. On 11 January 1794, the Spanish and British governments signed the Third Nootka Convention which called for the abandonment of all permanent settlements on Nootka Sound. Santa Cruz de Nuca was formally abandoned on 28 March 1795. The convention also stipulated that both nations were free to use Nootka Sound as a port and erect temporary structures, but, "neither ... shall form any permanent establishment in the said port or claim any right of sovereignty or territorial dominion there to the exclusion of the other. And Their said Majesties will mutually aid each other to maintain for their subjects free access to the port of Nootka against any other nation which may attempt to establish there any sovereignty or dominion". On 19 August 1796, Spain made the decision to join the French Republic in their war against Great Britain with the signing of the Second Treaty of San Ildefonso, thus ending Spanish and British cooperation in the Americas.
East of the Continental Divide, the Spanish Empire claimed all land south of the Arkansas River that was west of the Calcasieu River. The vast disputed region between the territorial claims of the United States and Spain was occupied primarily by native peoples with very few traders of either Spain or the United States present. In the south, the disputed region between the Calcasieu River and the Sabine River encompassed Los Adaes, the first capital of Spanish Texas. The region between the Calcasieu and Sabine rivers became a lawless no man's land. The United States saw great potential in these western lands, and hoped to settle their borders. Spain, seeing the end of New Spain, hoped to employ its territorial claims before it would be forced to grant Mexico its independence (later in 1821). Spain hoped to regain much of its territory after the regional demands for independence subsided.
Details of the treaty.
The treaty, consisting of 16 articles was signed in Adams' State Department office at Washington, on February 22, 1819, by John Quincy Adams, U.S. Secretary of State, and Luis de Onís, Spanish minister. Ratification was postponed for two years, because Spain wanted to use the treaty as an incentive to keep the United States from giving diplomatic support to the revolutionaries in South