The Adams-Onis Treaty was concluded with Spain 196 years ago today (1819). It ceded Florida to the United States and settled, after nearly 16 years, the boundary of the Louisiana Purchase between the U.S. and the Viceroyalty of New Spain.
His Catholic Majesty cedes to the United States, in full property and sovereignty, all the territories which belong to him, situated to the eastward of the Mississippi, known by the name of East and West Florida.
The boundary-line between the two countries, west of the Mississippi, shall begin on the Gulph 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 [Pacific].
The Treaty thereby negated U.S. claims to Texas — temporarily.
The Avalon Project has the complete text of the Treaty. The Adams in the Treaty short name is Secretary of State John Quincy Adams. Onis is Luis de Onís y Gonzalez-Vara of Spain. It’s also known as the Transcontinental Treaty,