Which treaty permanently opened New Orleans to American trade?

Pinckney's Treaty, also known as the Treaty of San Lorenzo, was signed in 1795 between the United States and Spain. This treaty is significant because it granted the United States the right to navigate the Mississippi River and established New Orleans as a key trading port for American merchants. Prior to this treaty, American access to the port and the river was contentious, primarily due to Spanish control.

The treaty was instrumental in promoting trade and economic growth in the new nation, as it allowed American farmers and traders to transport their goods freely down the Mississippi River to export at New Orleans without the fear of Spanish restrictions. This access was crucial for the westward expansion of the United States and was a significant factor leading toward the eventual acquisition of more territory in North America.