The U.S. Navy first established a naval base at Key West in 1823 for the suppression of piracy in the Caribbean Sea and the Gulf of Mexico.

During the Civil War, Key West was the headquarters of the U.S. Navy's East Gulf Blockading Squadron, which was responsible for the blockade of the Florida peninsula from Cape Canaveral on the Atlantic coast to St. Andrew Bay in the Gulf of Mexico.

One of the surviving buildings used by the Union navy during the Civil War is the United States Marine Hospital at 401 Emma Street designed by Robert Mills, designer of the Washington Monument. This building was constructed in 1845 and was used for treatment of Union military personnel including victims of the yellow fever epidemics which swept Key West during the Civil War.

Clinton Square Market, located at 291 Front Street, also survives and was constructed between 1856-1861 for use by the Union navy as a coal depot and storehouse for its vessels on blockading duty.

Information provided by the Florida Division of Historical Resources, a division of the Florida Department of State