Newly declassified documents from the US Defense Department show how many nuclear weapons the United States deployed at sea between 1953 and 1991. The documents, which give totals for the Atlantic Ocean, Pacific Ocean, and Mediterranean Sea, show that the number of US nuclear weapons afloat peaked in 1975 at 6,191 warheads, at the time nearly 23 percent of the US nuclear weapons stockpile. From 1974 to 1991, US fleets at sea routinely carried more than 5,000 nuclear weapons in total, or approximately 20 percent of the entire nuclear weapons stockpile. In 1991, US President George H. W. Bush decided to off-load all nonstrategic nuclear weapons from the fleet, a task completed in 1992. The number of US nuclear weapons currently at sea remains an official secret, but the authors have estimated the number of deployed warheads on ballistic missiles to create an extended timeline through 2015.