Perhaps no other issue caused such sectional divisiveness during the Confederation Period than the right to navigate the Mississippi River. The Treaty of Paris (1783) had stipulated that the Mississippi would be the western boundary of the United States and that it would be open to Americans for navigation. When Spain closed the river to Americans in 1784, southerners were bellicose and threatened war. The Spanish diplomat Don Diego de Gardoqui arrived in the United States in 1786 and began negotiations with Secretary for Foreign Affairs John Jay. When news broke of Congress’ authorizing Jay to abandon the American right to navigate the river for twenty years, the reaction was swift and bitter. Southern delegates in Congress argued that the river was a commercial life line for their economy. Westerners even threatened to raise troops and drive the Spanish out of the region. Northerners were no less strident. They flirted with the idea of a Northern confederacy since westerners and southerners represented blocs unwilling to temporarily give up navigation rights in order to secure a commercial treaty with Spain immediately that would benefit the Northern States. Outside Congress the press kept the issue in the forefront leading John Marshall to note that leaders like Patrick Henry would rather “part with the confederation than to relinquish the navigation of the Mississippi.” When the Philadelphia Convention considered commercial matters, the southern delegates, viewing the Mississippi crisis as a lesson, demanded a two-thirds vote when ratifying treaties. A two-thirds majority gave southern states veto power over any treaty that endangered their interests.
The United States, Spain, and the Navigation of the Mississippi River (pdf) taken from Commentaries on the Constitution, Vol. XIII has a fuller explanation of the problems associated with this diplomatic crisis in 1785-1787. The selections below illustrate how the issue was of particular importance to Americans while the Philadelphia Convention met.