Under the 1783 Treaty of Paris, which river became the United States’ western boundary?

Under the 1783 Treaty of Paris, the Mississippi River became the United States’ western boundary.

The treaty defined the new nation’s western boundary as the Mississippi River, separating the United States from Spanish Louisiana and other territories west of the river. The boundary extended northward toward the Great Lakes, while the northern border with British North America followed lines connected with those lakes and waterways.

This arrangement gave the United States a vast territory even though much of the land west of the Appalachian Mountains was sparsely mapped by American officials. The river boundary also made access to the Mississippi and its port at New Orleans strategically important for the young republic.

The treaty’s map was not perfectly precise, and later disputes required additional agreements and surveys. The boundary should not be confused with the later Louisiana Purchase of 1803, which expanded United States territory west of the Mississippi. The 1783 treaty established the river as the western edge of the original United States after independence.