In the 1783 Treaty of Paris, the Mississippi River formed the western boundary of the newly recognized United States.
The treaty ended the American Revolutionary War and recognized the United States as free, sovereign, and independent. Its territorial terms gave the new nation land east of the Mississippi River, north of Spanish Florida, and south of British North America. The arrangement created a country much larger than the original Atlantic seaboard colonies.
The document also addressed fishing rights, debts, prisoners of war, and Loyalist property. Article Two described the boundaries in detail, but the wording created later geographic and diplomatic problems. In particular, a line west from the Lake of the Woods did not actually intersect the Mississippi as the negotiators apparently expected.
The treaty was signed in Paris on September 3, 1783, and the Confederation Congress ratified it on January 14, 1784. The Mississippi boundary should not be confused with the later Louisiana Purchase, which transferred French territory west of the river to the United States in 1803.