In 1791 Captain George Vancouver claimed the southern part of Western Australia for the British Crown. As he explored along the coast, he discovered one of the world's finest natural harbours and named it the Princess Royal Harbour and King George III Sound after King George III.

During the 19th century, the loss of this strategic port to any enemy naval squadron was recongised as a potential threat to the security of Australia. Consequently, as the first example of federation prior to federation all the Australian states agreed to proportionally pay for the construction of a fort with the Imperial British Government supplying the guns. The Fort was opened in 1893, the first federal defence of Australia - and today called the Princess Royal Fortress.

The Princess Royal Fortress is not a grand fort of battlements, towers and stone, for this was the age of protection by concealment. With two gun batteries dug into the hillside of Mt Adelaide - Fort Princess Royal (2 x 6” guns) and Fort Plantagenet (1 x 6” gun). The Albany Barracks housed a small permanent garrison to man the guns.

From 1893 to 1956 the guns of King George III Sound maintained their role as a deterrent never firing a shot in anger. It was neither age nor enemy which silenced the guns of the Sound but rather the advent of the missile era.

In 1956, throughout the Commonwealth, coastal defences like the Princess Royal Fortress were closed, dismantled and generally destroyed. The buildings were used as schoolrooms, migrant hostels and a holiday camp before becoming vacant and succumbing to vandalism.

It now houses a number of major museum display areas.