How Many and Where Were the Nukes? (18 Aug 2006) "What the U.S. Government No Longer Wants You to Know about Nuclear Weapons During the Cold War." National Security Archive Electronic Briefing Book No. 197 Edited by William Burr.

The National Security Archive says:

The Pentagon and the Energy Department have now stamped as national security secrets the long-public numbers of U.S. nuclear missiles during the Cold War, including data from the public reports of the Secretaries of Defense in 1967 and 1971, according to government documents posted today on the Web by the National Security Archive .

Among the documents censored: U.S. Department of Defense, Annual Report for Fiscal Year 1964 (Washington, D.C., Government Printing Office, 1966).