Joining the United States; Indian removal

See also: Florida Territory and Seminole Wars

Defense of Florida's northern border with the United States was minor during the second Spanish period. The region became a haven for escaped slaves and a base for Indian attacks against U.S. territories, and the U.S. pressed Spain for reform.
Americans of English descent and Americans of Scots-Irish descent began moving into northern Florida from the backwoods of Georgia and South Carolina. Though technically not allowed by the Spanish authorities, the Spanish were never able to effectively police the border region and the backwoods settlers from the United States would continue to migrate into Florida unchecked. These migrants, mixing with the already present British settlers who had remained in Florida since the British period, would be the progenitors of the population known as Florida Crackers.^[27]
These American settlers established a permanent foothold in the area and ignored Spanish officials. The British settlers who had remained also resented Spanish rule, leading to a rebellion in 1810 and the establishment for ninety days of the so-called Free and Independent Republic of West Florida on September 23. After meetings beginning in June, rebels overcame the Spanish garrison at Baton Rouge (now in Louisiana), and unfurled the flag of the new republic: a single white star on a blue field. This flag would later become known as the "Bonnie Blue Flag".
In 1810, parts of West Florida were annexed by proclamation of President James Madison, who claimed the region as part of the Louisiana Purchase. These parts were incorporated into the newly formed Territory of Orleans. The U.S. annexed the Mobile District of West Florida to the Mississippi Territory in 1812. Spain continued to dispute the area, though the United States gradually increased the area it occupied.
Seminole Indians based in East Florida began raiding Georgia settlements, and offering havens for runaway slaves. The United States Army led increasingly frequent incursions into Spanish territory, including the 1817–1818 campaign against the Seminole Indians by Andrew Jackson that became known as the First Seminole War. The United States now effectively controlled East Florida. Control was necessary according to Secretary of State John Quincy Adams because Florida had become "a derelict open to the occupancy of every enemy, civilized or savage, of the United States, and serving no other earthly purpose than as a post of annoyance to them.".^[28]
Florida had become a burden to Spain, which could not afford to send settlers or garrisons. Madrid therefore decided to cede the territory to the United States through the Adams-Onís Treaty, which took effect in 1821.^[29] President James Monroe was authorized on March 3, 1821 to take possession of East Florida and West Florida for the United States and provide for initial governance.^[30] Andrew Jackson, on behalf of the U.S. federal government, served as a military commissioner with the powers of governor of the newly acquired territory for a brief period.^[31] On March 30, 1822, the U.S. Congress merged East Florida and part of West Florida into the Florida Territory.^[32]

A contemporaneous depiction of the New River Massacre in 1836.

By the early 1800s, Indian removal was a significant issue throughout the southeastern U.S. and also in Florida. In 1830, the U.S. Congress passed the Indian Removal Act and as settlement increased, pressure grew on the United States government to remove the Indians from Florida. Seminoles harbored runaway blacks, known as the Black Seminoles, and clashes between whites and Indians grew with the influx of new settlers. In 1832, the Treaty of Payne's Landing promised to the Seminoles lands west of the Mississippi River if they agreed to leave Florida. Many Seminole left at this time.
Some Seminoles remained, and the U.S. Army arrived in Florida, leading to the Second Seminole War (1835–42). Following the war, approximately 3,000 Seminole and 800 Black Seminole were removed to Indian Territory. A few hundred Seminole remained in Florida in the Everglades.

A Cracker cowboy, 19th century.

On March 3, 1845, Florida became the 27th state to join the United States of America.^[33] The state was admitted as a slave state and ceased to be a sanctuary for runaway slaves. Initially its population grew slowly.
As European-American settlers continued to encroach on Seminole lands, and the United States intervened to move the remaining Seminoles to the West. The Third Seminole War (1855–58) resulted in the forced removal of most of the remaining Seminoles, although hundreds of Seminole Indians remained in the Everglades.^[34]

Slavery, war, and disenfranchisement

Further information: Florida in the American Civil War

The Battle of Olustee during the American Civil War, 1864.

American settlers began to establish cotton plantations in northern Florida, which required numerous laborers, which they supplied by buying slaves in the domestic market. By 1860 Florida had only 140,424 people, of whom 44% were enslaved. There were fewer than 1,000 free African Americans before the American Civil War.^[35]
In January 1861, nearly all delegates in the Florida Legislature approved an ordinance of secession, declaring Florida to be "a sovereign and independent nation"—an apparent reassertion to the preamble in Florida's Constitution of 1838, in which Florida agreed with Congress to be a "Free and Independent State." Although not directly related to the issue of slavery, the ordinance declared Florida's secession from the Union, allowing it to become one of the founding members of the Confederate States, a looser union of states.
The confederal union received little help from Florida; the 15,000 men it offered were generally sent elsewhere. The largest engagements in the state were the Battle of Olustee, on February 20, 1864, and the Battle of Natural Bridge, on March 6, 1865. Both were Confederate victories.^[36] The war ended in 1865.
Following the American Civil War, Florida's congressional representation was restored on June 25, 1868, albeit forcefully after Radical Reconstruction and the installation of unelected government officials under the final authority of federal military commanders. After the Reconstruction period ended in 1876, white Democrats regained power in the state legislature. In 1885 they created a new constitution, followed by statutes through 1889 that disfranchised most blacks and many poor whites.^{[citation needed]}
Until the mid-20th century, Florida was the least populous Southern state. In 1900 its population was only 528,542, of whom nearly 44% were African American, the same proportion as before the Civil War.^[37] The boll weevil devastated cotton crops.
Forty thousand blacks, roughly one-fifth of their 1900 population, left the state in the Great Migration. They left due to lynchings and racial violence, and for better opportunities.^[38] Disfranchisement for most African Americans in the state persisted until the Civil Rights Movement of the 1960s gained federal legislation in 1965 to enforce protection of their constitutional suffrage.