Adams–Onís Treaty

The 1819 agreement in which Spain ceded Florida to the United States and the two countries defined a boundary between U.S. and Spanish territory in North America.

First Seminole War: A U.S. military campaign in Spanish Florida in 1817–1818, led by Andrew Jackson against Seminole communities and fugitive settlements. Jackson’s invasion of Spanish Florida intensified pressure for Spain to resolve the territory’s status.
Transcontinental Treaty: The common name for the agreement signed by the United States and Spain in 1819 and ratified in 1821. This is the treaty’s formal alternative name, emphasizing its continental boundary provisions.
Florida Territory: A U.S. territory established in 1822 from the former Spanish colony of Florida. The treaty’s transfer of Florida enabled its organization as a U.S. territory.
Pinckney's Treaty: A 1795 agreement between the United States and Spain that settled border and navigation disputes. It preceded the treaty and had already defined part of the U.S.–Spanish boundary.
Andrew Jackson: U.S. military commander and politician who later became the seventh president of the United States. His 1818 campaign in Florida helped force negotiations with Spain.
Sabine River: A river forming part of the boundary between Texas and Louisiana before flowing into the Gulf of Mexico. The treaty used it as the eastern starting point of the U.S.–Spanish boundary.
Florida Statehood: Florida’s admission to the United States as its twenty-seventh state in 1845. The cession began the process that eventually brought Florida into the Union.
Louisiana Purchase: The 1803 U.S. acquisition of France’s claim to a vast territory west of the Mississippi River. Its unclear limits contributed to disputes that the treaty sought to settle.
John Quincy Adams: U.S. diplomat and politician who served as secretary of state and later became the sixth U.S. president. As secretary of state, he negotiated the agreement for the United States.
Red River of the South: A major river that flows across the southern Great Plains and joins the Mississippi River system. The treaty’s boundary followed it westward from the Sabine River.

Linked from 14 pages