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.

20th-century growth

Historically, Florida's economy was based upon agricultural products such as cattle farming, sugarcane, citrus, tomatoes, and strawberries.
Economic prosperity in the 1920s stimulated tourism to Florida and related development of hotels and resort communities. Combined with its sudden elevation in profile was the Florida land boom of the 1920s, which brought a brief period of intense land development. Devastating hurricanes in 1926 and 1928, followed by the Great Depression, brought that period to a halt. Florida's economy did not fully recover until the military buildup for World War II.
The climate, tempered by the growing availability of air conditioning, and low cost of living made the state a haven. Migration from the Rust Belt and the Northeast sharply increased Florida's population after the war. In recent decades, more migrants have come for the jobs in a developing economy.
With a population of more than 18 million according to the 2010 census, Florida is the most populous state in the Southeastern United States, and the fourth most populous in the United States.