The Port of Apalachicola was of primary strategic importance during the United States Civil War. Union forces established a blockade of the port on 11 June 1861, with the USS Montgomery. At times, the blockade employed a squadron of three or more vessels in the area. On 3 April 1862, a landing at Apalachicola was achieved without resistance from the Confederacy.
The port continued to change hands repeatedly throughout the war, usually without serious conflict.