Spanish Florida, comprising the provinces of East and West Florida, was ceded to the United States under the provisions of the “Treaty of Amity, Settlement, and Limits, between the United States of America and His Catholic Majesty,” of February 22, 1819. The treaty was signed in Washington by Secretary of State John Quincy Adams, and Louis de Onis, the Spanish Minister to the United States. Ratifications of the treaty were delayed, but on October 24, 1820, Ferdinand VII of Spain affixed his ratification and confirmation, while acceptance on the part of the United States Senate followed on February 19, Three days later, President Monroe approved the treaty, and proclaimed it in force.
Young, Rogers W.
"The Transfer of Fort San Marcos and East Florida to the United States,"
Florida Historical Quarterly: Vol. 14
, Article 3.
Available at: https://stars.library.ucf.edu/fhq/vol14/iss4/3