The Pinckney Treaty, officially called the Treaty of San Lorenzo, was signed by the United States and Spain on October 27, 1795, to end a dispute between the two countries over land settlement and Mississippi River trade. The agreement was brokered by American statesman Thomas Pinckney (1750–1828), then U.S. Special Commissioner to Spain. The treaty specified that Spain would recognize the 31st parallel (the northern border of present-day Florida) as the southern boundary of the United States, that Spain would allow American goods to land at New Orleans tax-free for a period of three years (with an option to renew), and that both countries would be allowed to use the Mississippi River freely.
The Pinckney Treaty represented significant gains for the United States during the administration of its first president, George Washington (1789–1797); lingering questions were settled between the two countries which had arisen since the United States won the American Revolution (1775–1783). These disputes had their roots in French concessions of the Louisiana Territory in 1762 and 1763. At that time, the Mississippi River became the western boundary of British colonies in the East and Spanish possessions in the West. When the United States won independence (1783), the Mississippi River became the new nation's western boundary. The Treaty of Paris (1783) granted transport rights along the Mississippi to the United States; but Spain, which had not been party to the treaty, later denied Americans the right to use the water route. Further, during the American Revolution, Spain had claimed—by right of conquest—territory along the Gulf of Mexico and along the eastern shore of the Mississippi, in the present-day states of Alabama, Mississippi, and Tennessee.
As American settlers moved onto Spanish lands, they found themselves in conflict with American Indians who had been incited by the Spanish. Meanwhile, the Spanish also tried gaining the confidence of frontiersmen in the West, who were increasingly dissatisfied with the U.S. federal government. Eventually Spain opened up the Mississippi to American traders in exchange for a 15 percent commission. Pressure thus mounted on Washington's administration to quell the insurgent frontiersmen, settle the boundary disputes, and negotiate free use of the Mississippi. Pinckney was dispatched to Madrid in 1794.
By the time Pinckney arrived to negotiate with Spain on behalf of the United States, in 1795, the diplomatic tides had turned in his favor. Spain's military was so weakened that Pinckney was not forced to make any concessions in exchange for those yielded by Spain to the United States. The treaty was a substantial victory for the new republic, and greatly contributed to westward settlement.