Florida became the 27th state of the Union on March 3, 1845. Although a constitution had been drafted in 1838, statehood was delayed because some Floridians wanted two states to be created from the territory and also because of Northern objections to the entrance of another slave-holding state. Like most southeastern states, Florida was a predominantly agricultural area, whose economy was based on the plantation system. When war between the states threatened over the slavery issue, Florida seceded from the Union on January 10, 1861, and joined the Confederacy. During the Civil War, Florida was an important supplier of food for the South. After the war, in 1868, it was restored to the Union, but the Reconstruction period did not end until 1876.

Florida's development had been limited and intermittent up to 1880. Its population lived mainly on farms, in rural towns, and in a few small coastal cities. Southern Florida was largely uninhabited. After 1880, however, the state's growth was striking. The growth was sparked by discovery of phosphate, development of cigar making, reclamation of swamps, production of citrus fruit, and railway construction. The railroads brought tourists, attracted by the pleasant climate and the magnificent hotels built by railroad developers such as Henry M. Flagler and Henry B. Plant. New lands in southern Florida were opened to settlers, farmers, and businessmen by the drainage of the Everglades, begun in 1906.

Following World War I, a real-estate boom brought millions of land speculators to the state. Overselling and overbuilding, however, led to collapse of the boom in 1926. The establishment of many new industries during and after World War II, together with an influx of tourists and retired persons, brought new prosperity. Opening of the Cape Canaveral missile complex in 1949 made Florida a major center of American space efforts.

After 1959 a critical problem was created by refugees who flooded into Florida, particularly the Miami area, from Cuba. A program for relocating the Cubans to other states as well as absorbing them into the Florida economy was adopted. Racial clashes between the state's white and black residents also became a problem in the 1960's.

In 1970 Seminoles in Florida and Oklahoma were awarded more than 12 million dollars by the federal government for land they had given up after the Seminole Wars. During the 1970's Florida's population increased by more than 40 per cent, one of the nation's highest growth rates. In 1980 a large number of refugees again arrived from Cuba. During the 1980's there was rapid economic expansion and continued population growth.

In the 1990's, hurricanes, especially Hurricane Andrew in 1992 and Hurricane Opal in 1995, caused billions of dollars in property damage in Florida. In the summer of 1998, wildfires burned across many areas of Florida.

Florida, like many other Southern states, became increasingly conservative politically during the 1980's and 1990's. As a result of the 1996 elections, Florida became the first state in the history of the South to have a Republican-controlled legislature. In 1999 Florida launched the first statewide school voucher program in the nation.

In 2004, from mid-August through September, Florida was struck by four major hurricanes. An estimated one in five houses was damaged or destroyed, causing some $20 billion in damage, and approximately 100 persons lost their lives.

Powerful hurricanes struck Florida in 2005. In August of that year, Hurricane Katrina devastated southern Florida. Another hurricane, called Hurricane Wilma, caused more death and destruction in Florida after it hit Florida's southwest coast in October.