Right after Florida given to the British as part of the treaties that ended The Seven Years War, they divided it into East and West Florida. The Spanish, after they gained back Florida after American Revolution, accepted the new boundaries and never really tried to exert control over Florida.
Soon, the northern part of the state became a haven for American settlers taking over land that belonged to Spain. By the early 1800s, the Napoleonic Wars were raging in Europe and in 1808, Spain was overrun by the French and the Spanish king forced to abdicate. Many Spanish colonies sought an opportunity to get out from under the rule of the Spanish crown. What also died in the French invasion was a U.S. offer to assume some Spanish debt in return ceding Florida. President Madison was afraid that the British would seize Florida and use it as a base against the U.S.
Settlers in the Mississippi Territory and western Florida Americans in the western part of the state took the matter into their own hands and declared the Free and Independent Republic of West Florida. They also appealed to President Madison to take over the territory. He responded by annexing the area claiming it was part of the Louisiana Purchase made in 1803.
Two years later in 1812, President Madison sent General George Matthews to East Florida to meet with the Spanish governor. His orders were negotiate an arrangement to take over East Florida. On his own, Matthews raised a force of Georgians and with the aid of nine U.S. Navy gunboats, seized Amelia Island just 50 miles north of St. Augustine, the Spanish territory’s seat of government for Florida. The rebels, known as “Patriots” declared they were the Republic of East Florida.
Alarmed and afraid the Spanish would react with force, President Madison convinced General Matthews to renounce the republic and return the land to Spain. However, before left Amelia Island in May 1813, Matthews convinced the Seminole king to remain neutral in the conflict between the U.S. and Britain.
However, many of the escaped slaves living amongst the Seminoles came from South Carolina and Georgia did not want to stay neutral. The war for control of Florida was not over. After the war of 1812 ended, British supported Seminoles continued to conduct raids into southern George. This led to the invasion of eastern Florida by General Andrew Jackson and what was known as the First Seminole War. By the end of 1818, the U.S. effectively controlled the east coast of Florida.
Spain realized they could no longer control Florida so in 1821 the U.S. took control of what is now the State of Florida through the Adams-Onis Treaty. East and West Florida were merged together and the capital Tallahassee was created because it was halfway between East Florida’s capital in St. Augustine and West Florida capital in Pensacola.
There were two more wars (II 1835 -1836 and III 1855 -1858) to force the Seminoles to move to reservations far to the west. In between them, Florida became the 27th state on March 25th, 1845.