3, 1783, Great Britain formally acknowledged the independence of the United States, and the warring European powers, Britain against France and Spain, with the Dutch as armed neutrals, effected a large-scale peace settlement. The Anglo-American settlement fixed the boundaries of the United States. In the Northeast the line extended from the source of the St. Croix River due north to the highlands separating the rivers flowing to the Atlantic from those draining into the St. Lawrence River, thence with the highlands to lat. 45N, and then along the 45th parallel to the St. Lawrence. From there the northern boundary followed a line midway through contiguous rivers and lakes (especially the Great Lakes) to the northwest corner of the Lake of the Woods, thence "due west- to the sources of the Mississippi (which were not then known).
The Mississippi, south to lat. 31N, was made the western boundary. On the south the line followed the 31st parallel E to the Chattahoochee River and its junction with the Flint River, then took a straight line to the mouth of the St. Marys River, and from there to the Atlantic. The navigation of the Mississippi was to be open to the citizens of both nations.
Under the British (1763-83), Florida was divided into two provinces, and St. Augustine and Pensacola were respectively made the capitals of East Florida and West Florida. Under the Treaty of Paris (1783), Florida was returned to Spain. Many colonists in Florida abandoned the region and moved to British possessions in the West Indies. Spain's hold over Florida, however, was extremely tenuous. Boundary disputes developed with the United States (see West Florida Controversy). In the War of 1812, Pensacola served as a British base until captured (1814) by U.S. General Andrew Jackson. In 1819, after years of diplomatic wrangling, Spain reluctantly signed the Adams-Onis treaty ceding Florida to the United States in return for U.