During the early Cold War, the Canadian government adivsed public that they could cheaply build fallout shelters in their homes to protect their families from radiation after a nuclear war. Publicly, the government stayed out of the shelter-building business, citing the cost was too high. However, from 1959 to the mid-1960s, the Canadian Army secretly constructed a network of 2,000 fallout shelters in government building: the Nuclear Detonation and Fallout Reporting System. This article explores the origins of this network and the reasons for its decline.