The Adams-Onis Treaty (or Transcontinental Treaty) of 1819 is significant in the expansion of the United States for adding the Florida territory to the country at relatively little cost and for giving the United States its first internationally recognized claim to territory on the Pacific Ocean.
Spain had established its control of the territory of Florida, which included the entire Gulf of Mexico shore from the Mississippi River to the current state of Florida, in the early 16th century. In 1763 Spain was forced to cede control to England after being on the losing side in the Seven Years’ War, but the Treaty of Paris ending the American Revolution restored Spanish authority in Florida. After making the Louisiana Purchase in 1803, however, the United States slowly began to seize pieces of Florida from Spain. Settlers occupied the area around Baton Rouge in 1810, prompting its annexation to the United States. The
U. S. Army then occupied Mobile Bay and other parts of West Florida during the War of 1812, ostensibly to keep those lands from falling into British hands. In 1818 General Andrew Jackson, on the pretext of fighting Seminole Indians who were raiding the southern United States from Florida, occupied much of the rest of the territory. Meanwhile, there was an ongoing dispute between the United States and Spain concerning the boundary of the Louisiana Purchase. The United States claimed that the Louisiana Purchase territory extended to the Rio Grande; the Spanish rejected this, asserting the Sabine River as the boundary.
Negotiated by Secretary of State John Quincy Adams with Luis de Onis, the Spanish ambassador in the United States, the Adams-Onis Treaty contained several provisions. First and foremost, the Spanish relinquished all claim to Florida. Additionally, the treaty settled the southwestern boundary of the Louisiana Purchase at the Sabine River. In exchange for the United States, accepting the Spanish interpretation of the Louisiana boundary, Spain relinquished its claims to the Oregon Territory in the Pacific Northwest, fixing the boundary between United States and Spanish territory on the Pacific coast at the 42nd parallel. Oregon remained disputed territory, however, as the United States and England had agreed to joint occupation in the Convention of 1818; the boundary between the United States and Canada in the Northwest would not be settled until the Oregon Treaty of 1846. Finally, although the United States did not “buy” Florida from Spain, the Adams-Onis Treaty relieved the Spanish government of $5 million worth of monetary claims made by American citizens against it. No actual money changed hands between the two countries.
The U. S. Senate readily ratified the treaty in 1819, though some criticism of Adams emerged for surrendering Texas when Onis might have been induced to cede that land as well. The Spanish, however, delayed ratification, hoping to secure a promise from the United States not to aid revolutions in Spanish colonies in Latin America. The United States demurred, and two years later, after Spain accepted the original treaty, the Senate ratified the treaty again on Washington’s birthday in 1821.
Further reading: Bradford Perkins, The Creation of a Republican Empire, vol. 1 of The Cambridge History of American Foreign Relations, 1776-1865, ed. Warren I. Cohen, general editor (New York: Cambridge University Press, 1993).
—Russell L. Johnson
World History
