At the end of the Seven Years War, Spain ceded Florida to Great Britain who established two colonies – East and West Florida. The boundaries were set as the Atlantic Coast on the east and the Mississippi River on the west. The northern boundary was set at 320 22′ North latitude.
This became an issue after the 1783 Treaty of Paris was signed. In it, Great Britain ceded the new United States the land east of the Mississippi to the Atlantic Coast south of the Canadian border and north of Florida. As part of the, both East and West Florida were returned to Spain.
At the time, Florida’s western border was the Mississippi River. However, the northern border of East and West Florida was not well surveyed, nor was the colony well settled. Complicating the issue was that most of the colonies (now states) assumed their western borders were the Mississippi. One of those was Georgia.
The 320 22′ line was well north of Georgia’s claimed southern border. To resolve the issue, George Washington sent Thomas Pickney to Madrid to negotiate a settlement. The U.S. claim assumed the land north of 310 North was British territory that was given to the U.S. by the Treaty of Paris.
Pickney got the Spanish to agree to a document that goes by three names – The Treaty of San Lorenzo, the Madrid Treaty or Pickney’s Treaty. Signed on October 27th, 1795, it became effective on August 3rd, 1796. It is the first territorial acquisition by the U.S.
Article I of the document sets the northern border of Florida as the 31st parallel. The treaty adjusted the boundaries for rivers in the east that account for Georgia’s unique geography at its southeastern end.
Article II guaranteed the U.S. would have access to the Mississippi River. At the time, Spain controlled the mouth of the river and Pickney’s Treaty put the U.S. in compliance with the 1783 Treaty of Paris that guaranteed the British access to the Mississippi River.
In the third article, the U.S. and the Spanish agreed to jointly survey the land. Article IV of the treaty set the western border of U.S. Territory as the middle of the Mississippi River. At the time Pickney’s Treaty was signed, Spain still had title to the land that became the Louisiana Purchase and did provide title to the French until just before the U.S./French deal to purchase the land closed. (See 8/11/21 post –What Did Jefferson Really Buy – https://marcliebman.com/what-did-jefferson-really-buy/ ).
Article IV was interesting, given the experience the U.S. was already having with the British. Through this clause, Spain agreed not to supply weapons or incite any of the Native American tribes living in the land given to the U.S.
In Articles VI and VII, the two countries agreed not to embargo citizens, ships, or cargo of the other nation and to protect and defend the other’s vessels within their territorial waters.
Pickney’s Treaty gave the U.S. a chunk of land that ultimately became parts of Alabama and Mississippi. Florida’s boundaries and land again became the subject of the U.S.’s next major land acquisition, known as the Louisiana Purchase.
Map of the territory acquired via Pickney’s Treaty.