Postcard depicting a moat around a fort on an island. The caption reads, ‘Old Fort Jefferson on Dry Tortugas, near Key West, Florida’. The description on the verso reads, 'This old Citadel, now Fort Jefferson National Monument, was a formidable coastal defense about the time of the American Civil War. Following termination of hostilities the Fortress was used as a Federal Prison and became known as the American Devil's Island. Here Dr. Samuel Mudd of Maryland was imprisoned for giving medical aid to John Wilkes Booth, assassin of President Lincoln.'