between the Mississippi and Perdido rivers, remained disputed between the two nations. In 1810, the Republic of West Florida successfully declared its independence from a weakened Spain. Ninety days later, U.S. military forces entered its capital (St. Francisville, Louisiana) and effectively annexed the short-lived nation. However, this action did not extend all the way to the Perdido River. During the War of 1812 (1812–15), U.S. military forces entered Mobile to enforce the surrender of the Spanish officials there. A year or so later, U.S. garrisons were defending Gulf coast forts against British naval attacks and attempting to stop the British Army from capturing New Orleans. This coastal area (today's Mississippi and Alabama Gulf coasts), the land west of the Perdido River, was incorporated into the Mississippi Territory by the United States. In 1817 the Alabama Territory was carved out of the eastern half of the Mississippi Territory. The dispute with Spain was finally resolved in 1819 with the Adams-Onís Treaty, in which Spain ceded all of Florida to the United States. The treaty wasn't ratified by the Spanish government until a couple of years later. In 1822 the Florida Territory was established, with the Perdido River as the (coastal) boundary between it and the new state of Alabama. References External links Perdido River Watershed - Florida DEP Rivers of Baldwin County, Alabama Bodies of water of Escambia County, Alabama Bodies of water of Escambia County, Florida Rivers of Alabama Rivers of Florida Outstanding Florida Waters Borders of Alabama Borders of Florida