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The Adams-Onis Treaty

aka the Transcontinental Treaty

After the Louisiana Purchase in 1803, President Thomas Jefferson argued that Florida was included in Louisiana. In 1810 and 1812 the United States annexed sections of West Florida. When John Quincy Adams became Secretary of State in 1817, he sought additional territory. In 1817 and 1818 Adams and President James Monroe resumed efforts to acquire Florida and a western boundary for the Louisiana Purchase. When Andrew Jackson attacked the Seminoles in East Florida in 1818, Spain, weakened by wars in Europe and colonial uprisings in Latin America, was powerless to defend the Floridas. She was also worried about the vagueness of the boundary between the United States and Spanish Mexico. Spain feared that American troops would invade Spanish Mexico from the Louisiana Territory, which the United States had purchased from France in 1803. Although Spain had previously refused to even discuss the purchase of Florida with the United States, she finally decided it was in her best interests to accept the terms presented by the United States.

The Transcontinental Treaty was signed by U.S. Secretary of State John Quincy Adams and Spanish Minister to the United States Don Luis de Onis on February 22, 1819. Under its terms, Spain ceded East Florida to the United States and renounced all claims to West Florida and the Oregon Country, in exchange for which the United States agreed to pay $5,000,000. The treaty also established a boundary between Mexico and the United States extending from the Gulf of Mexico northward and then westward along the banks of the Sabine, Red, and Arkansas rivers, then westward along the 42nd parallel to the Pacific Ocean. By this treaty, the United States recognized Spanish claims to what are now Texas, New Mexico, Arizona, Colorado, Nevada, Utah, and California. The treaty was approved by the U.S. Senate on February 24, 1819, but Spanish authorities delayed their approval until 1821. The Senate then ratified the treaty a second time, and President James Monroe exchanged copies with Spanish authorities in February of 1821.

The exact boundary between the United States and Mexico was specified in the Adams-Onis Treaty as follows:
The Boundary Line between the two Countries, West of the Mississippi, shall begin on the Gulf of Mexico, at the mouth of the River Sabine in the Sea, continuing North, along the Western Bank of that River, to the 32d degree of Latitude; thence by a Line due North to the degree of Latitude, where it strikes the Rio Roxo of Nachitoches, or Red-River, then following the course of the Rio-Roxo Westward to the degree of Longitude 100 West from London and 23 from Washington, then crossing the said Red-River, and running thence by a Line due North to the River Arkansas, thence, following the Course of the Southern bank of the Arkansas to its source in Latitude 42 North and thence by that parallel of Latitude to the South-Sea.

map showing the border between the U.S. and Mexico as outlined by the Adams-Onis Treaty

See Also

Louisiana Purchase
President Thomas Jefferson
President James Monroe
Andrew Jackson
John Quincy Adams
New Mexico

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This page was last updated on December 02, 2018.