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 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.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".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.[9] 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.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.To the west of New Orleans, the United States assumed the French claim to all land east and north of either the Sabine River[15] or the Rio Grande.[18][19][20] 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[notes 2] in 1792–1793, and (4) the exploration of David Thompson in 1807–1812.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.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".[21] 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.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 America.The previous Anglo-American Convention of 1818 meant that both American and British citizens could settle land north of the 42nd parallel and west of the Continental Divide.The United States now had a firm foothold on the Pacific Coast and could commence settlement of the jointly occupied Oregon Country (known as the Columbia District to the British government).Many historians consider the Treaty to be a great achievement for the U.S., as time validated Adams's vision that it would allow the U.S. to open trade with the Orient across the Pacific.By the mid-1830s, a controversy developed regarding the border with Texas, during which the United States demonstrated that the Sabine and Neches rivers had been switched on maps, moving the frontier in favor of Mexico.Upon statehood in 1850, California established the 42nd parallel as its constitutional de jure border as it had existed since 1819 when the territory was part of Spanish Mexico.
Portion of West Florida that was claimed by the United States.