Following Abraham Lincoln's election in 1860, the state of Florida joined other Southern states in declaring secession from the Union. Florida was the third of the original seven states to do so. (The first state to secede was South Carolina, the second Mississippi.)
With a small population, Florida would contribute more goods to the Confederate cause than manpower. It produced large amounts of sustenance and its large coastline made it difficult for Union Navy efforts to curb blockade runners bringing in supplies and material from foreign markets to support the Confederate war effort.
As Florida was an important supply route for the Confederate Army, Union forces operated a blockade around the entire state. Union troops occupied major ports such as Cedar Key, Jacksonville, Key West, and Pensacola early in the war. Confederate forces moved quickly to seize control of many of Florida's U.S. Army forts, succeeding in most cases, with the significant exceptions of Fort Jefferson, Fort Pickens and Fort Zachary Taylor, which stayed firmly in Federal control throughout the war.
Governor John Milton, an ardent secessionist, throughout the war stressed the importance of Florida as a supplier of goods. Florida was a large provider of food (particularly beef cattle) and salt for the Confederate Army. The 8,436-mile coastline and 11,000 miles of rivers, streams, and waterways proved a haven for blockade runners and a daunting task for patrols by Federal warships.
The state's small population (140,000 residents making it last in size in the Confederacy) and relatively remote location, proved both a blessing and a curse to both sides throughout the war.
Overall, the state raised some 15,000 troops (more than 10% of its population) for the Confederacy, which were organized into twelve regiments of infantry and two of cavalry, as well as several artillery batteries and supporting units. Most of these troops were sent to serve in the Army of Northern Virginia under Brig. Gen. Edward A. Perry and Col. David Lang. The "Florida Brigade" fought in many of Robert E. Lee's campaigns, and twice charged Cemetery Ridge during the Battle of Gettysburg, including supporting Pickett's Charge.
In early 1862, the Confederate government pulled General Braxton Bragg's small army from Pensacola following successive Confederate defeats in Tennessee at Fort Donelson and Fort Henry and the fall of New Orleans. It sent them to the Western Theater for the remainder of the war. The only Confederate forces remaining in Florida at that time were a variety of independent companies, several infantry battalions, and the 2nd Florida Cavalry. They were reinforced in 1864 by troops from neighboring Georgia.
Numerous small skirmishes occurred in Florida -- including the battles of Natural Bridge, Gainesville, Marianna, Vernon and Fort Brooke. The major engagement was at Olustee near Lake City. Union forces under General Truman Seymour were repulsed by Florida and Georgia troops and retreated to their fortifications around Jacksonville. Seymour's relatively high losses caused Northern lawmakers and citizens to question the necessity of any further Union actions in Florida. Many of the Federal troops were withdrawn and sent elsewhere. Throughout the balance of 1864 and into the following spring, the 2nd Florida Cavalry repeatedly thwarted Federal raiding parties into the Confederate-held northern and central portions of the state.
In early May 1865, Edward M. McCook's Union division was assigned to re-establish Federal control and authority in Florida. Governor Milton committed suicide rather than submit to Union occupation. On May 13, Col. George Washington Scott surrendered the last active Confederate troops in the state to McCook. On May 20, Tallahassee was the next to last Confederate state capital to fall to the Union army. Austin, Texas fell the next month.
Florida would not "rejoin" the Union or be "readmitted" to the United States until July 25, 1868.