Fort Denison was originally a small, rocky island referred to by Aboriginal people as Mat-te-wan-ye. After the arrival of the First Fleet in 1788, Governor Phillip renamed the land Rock Island, however informally it was known as Pinchgut, as it was believed convicts were sentenced to weeks of isolation on the island with very little food and water. In late 1796 the Governor installed a gibbet on the island – gibbeting is the practice of displaying a recently executed person as a deterrent for other criminals – with Francis Morgan one of the first to succumb to this practice on Pinchgut. He was convicted and hanged for murder, with his skeleton hanging on the island for years after his execution.
In 1839 when two American warships entered the harbour at night and circled the island, concern for foreign attack was heightened and forced the government to review their defenses. The suggestion was put forward to turn the island into a fort to protect Sydney Harbour. The island was quarried for sandstone which was used to build Bennelong Point where the Opera House now stands. Once it was flattened the construction of a fortification commenced in 1841 but was not completed. It resumed in 1855 due to fear of Russian naval attack during the Crimean War and was completed on the 14 November 1857. Fort Denison derives its name from Sir William Thomas Denison, the then Governor of New South Wales.
The fortress features a distinctive Martello tower, the only one to ever be built in Australia and the last one ever constructed in the British Empire. Developments in artillery rendered the fortress fairly obsolete by the time it was completed. Its armament included three eight inch muzzle loaders in the tower, two ten inch guns, one on a 360 degree traverse on the top of the tower and one in a bastion at the other end of the island, and twelve thirty-two pound cannons in a battery between the base of the tower and the flanking bastion. Eventually all guns were removed except for the three muzzle – loading cannons in the tower.
In October 1900, during the Boer War in Africa, the White Star Line ship SS Medic sailed into Sydney Harbour and dropped anchor in Neutral Bay. One evening the fourth officer Charles Lightoller and two of his shipmates rowed out to Fort Denison intending to fool people into thinking a Boer raiding party was attacking Sydney by hoisting a makeshift Boer flag on the lightning conductor. They fired a harmless wad of cotton waste from one of the canons which shattered a few windows. Lightoller was never apprehended but confessed all in an autobiography. He was transferred to the Atlantic and went on to be the second officer on the RMS Titanic and the most senior officer to survive the 1912 sinking. He was a key witness into the disaster.
In 1913 a lighthouse beacon built in Birmingham, England was shipped to Sydney and replaced the gun of the rood of the tower. This light is still in use today. In May 1942 three Japanese two-man midget submarines attacked Sydney Harbour. When the the US Navy cruiser USS Chicago fired on the Japanese, some of its five inch shells hit Fort Denison, causing the tower minor damage which can be seen today.
During the 1990s a significant conservation and upgrade of the site occurred. Increased harbour traffic has already destroyed the slipway and the porous nature of the sandstone has seen the salt wear down the fort’s foundations. The island now operates as a major tourist attraction with a museum, restaurant and events. The custom of firing a gun daily at 1pm began in 1906 to enable sailors to set their ships chronometers correctly. This tradition continued until the Second World War when it was stopped so as not to fear residents. The practice recommenced in 1986 and is still done today.