In 1958, at the height of the Cold War and the infancy of the Intercontinental Ballistic Missile (ICBM) threat, John Diefenbaker, Canada's Prime Minister at the time, authorized the creation of close to 50 Emergency Government Headquarters (called Diefenbunkers by opposition parties across Canada. These shelters were part of what came to be known as the Continuity of Government plan, which was meant to protect various members of government in the event of a nuclear attack.
The Carp shelter would be the largest of such facilities (over 9,300 m2 (100,000 sq ft) and the only one in the immediate Ottawa area. The underground 4-story bunker required 32,000 tonnes of concrete and 5,000 tonnes of steel. The structure was capable of withstanding a nuclear blast up to 5 megatons from 1.8 km (1.1 mi) away. It had massive blast doors at the surface, as well as extensive air filters to prevent radiation infiltration.

Underground storage was built for food, fuel, fresh water, and other supplies. The bunker was built to accommodate 565 people for up to one month without receiving additional supplies from the outside. It included an emergency broadcast studio for the Canadian Broadcasting Corporation and a vault on the lowest level to hold the gold reserves of the Bank of Canada.

Construction began in 1959 in an abandoned gravel pit outside Carp, and was completed by 1962. The blast tunnel entrance. The doors to the actual bunker are perpendicular to this tunnel which reduces the effects of a nuclear shock wave.

These facilities were administered by the Royal Canadian Corps of Signals (later the Communications and Electronics Branch). A decentralized transmitter site, the Richardson Detachment, with numerous transmitter antenna was located further to the west near Perth Ontario that was supported from a 2 storey underground facility of similar construction to the Carp facility but much smaller. Two radio receiving facilities, the CFS Carp Almonte Detachment and CFS Carp Dunrobin Detachment, with a complete receiving antenna arrays were built in the region but all buildings were above ground.

CFS Carp was decommissioned in 1994 following the reduction in the ICBM threat.

From 1959 to 1994, the site was owned and operated by the Government of Canada, Department of National Defence. After the local municipality took control of the facility in 1994, the community took a great interest in the bunker, requesting access to public tours of the facility. The local municipality took control of the facility and a group of local volunteers, recognizing the heritage and tourism value of the Carp Diefenbunker, undertook to open the facility as a cold war museum and conduct public tours. It was purchased by the Diefenbunker Development Group in 1998, and officially opened as a museum. The name of the facility was changed to the Diefenbunker, Canada's Cold War Museum shortly thereafter. It is currently open year-round for public tours.

More information can be found here: http://diefenbunker.ca/