Who Controlled the Mississippi River Border from Florida? No Single Authority Existed

The premise contains a geographic confusion: Florida and the Mississippi River are separated by ~500 miles and multiple jurisdictions. No single entity ever controlled a "border between Florida and the Mississippi River" because they don't share a border.

Historical Control of the Mississippi

• France (1682–1763): La Salle claimed the entire Mississippi basin (Louisiana).
• Spain (1763–1800/1803): West bank (including New Orleans) after Seven Years' War.
• Britain (1763–1783): East bank (incl. West Florida) after same war.
• USA (1783/1803–present): East bank 1783; entire river via Louisiana Purchase (1803).

Florida's Separate History

• Spanish (1513–1763, 1783–1821).
• British (1763–1783) – split into East/West Florida.
• US Territory (1821), State (1845).

The Real Border

The Mississippi River's eastern bank formed the western boundary of the US (1783), then of Spanish West Florida, then US again. But Florida's territory never extended to the river.