Nuclear Weapons 101
The United States was the first country in the world to develop nuclear weapons, and is the only country to have used them as actual weapons, during the two bombings of Hiroshima and Nagasaki in World War II. Before and during the Cold War it conducted over a thousand nuclear tests and developed many long-range weapon delivery systems. It maintains an arsenal of about 5,500 warheads to this day, as well as facilities for their construction and design, though many of the Cold War facilities have since been deactivated and are sites for environmental remediation.
The United States of America first began developing nuclear weapons during World War II under the order of President Franklin Roosevelt in 1939, motivated by a fear that they were engaged in a race with Nazi Germany to develop such a weapon. After a slow start under the direction of the National Bureau of Standards, at the urging of British scientists and American administrators the program was put under the Office of Scientific Research and Development, where in 1942 it was officially transferred under the auspices of the U.S. Army and became known as the Manhattan Project. Under the direction of General Leslie Groves, over thirty different sites were constructed for the research, production, and testing of components related to bomb making. These included the scientific laboratory, Los Alamos (in New Mexico), under the direction of physicist Robert Oppenheimer, a plutonium production facility, Hanford (in Washington), and a uranium enrichment facility, Oak Ridge (in Tennessee).
By investing heavily both in breeding plutonium in early nuclear reactors, and in both the electromagnetic and gaseous diffusion enrichment processes for the production of uranium-235, the United States was able by mid-1945 to develop three usable weapons. A plutonium-implosion design weapon was tested on 16 July 1945 ("Trinity"), with around a 20 kiloton yield. On the orders of President Harry S. Truman, on 6 August of the same year a uranium-gun design bomb ("Little Boy") was used against the city of Hiroshima, Japan, and on 9 August a plutonium-implosion design bomb ("Fat Man") was used against the city of Nagasaki, Japan. The two weapons killed approximately 250,000 Japanese civilians outright, and thousands more have died over the years from radiation sickness and related cancers.
During the Cold War
Between 1945 and 1990, more than 70,000 total warheads were developed, in over 65 different varieties, ranging in yield from around .01 kilotons to the 25 megaton B41 bomb.
Between 1940 and 1996, the U.S. spent at least $5.8 trillion (in 1996 dollars) on nuclear weapons development. Over half of this was spent on building delivery mechanisms for the weapon. $365 billion was spent on nuclear waste management and environmental remediation.
After the end of the Cold War following the dissolution of the Soviet Union in 1991, the U.S. nuclear program was heavily curtailed, halting its program of nuclear testing, ceasing in the production of new nuclear weapons, and reducing its stockpile by half by the mid-1990s under President Bill Clinton. Many of its former nuclear facilities were shut down, and their sites became targets of extensive environmental remediation. Much of the former efforts towards the production of weapons became involved in the program of stockpile stewardship, attempting to predict the behavior of aging weapons without using full-scale nuclear testing. Increased funding also was put into anti-nuclear proliferation programs, such as helping the states of the former Soviet Union eliminate their former nuclear sites, and assist Russia in their efforts to inventory and secure their inherited nuclear stockpile. As of February 2006, over $1.2 billion were paid under the Radiation Exposure Compensation Act of 1990 to U.S. citizens exposed to nuclear hazards as a result of the U.S. nuclear weapons program, and by 1998 at least $759 million was paid to the Marshallese Islanders in compensation for their exposure to U.S. nuclear testing, and over $15 million was paid to the Japanese government following the exposure of its citizens and food supply to nuclear fallout from the 1954 "Bravo" test.
During the presidency of George W. Bush, and especially after the 11 September terrorist attacks of 2001, rumors have circulated in major news sources that the U.S. has been considering design of new nuclear weapons ("bunker-busting nukes"), and potentially the resumption of nuclear testing for reasons of stockpile stewardship, and non-nuclear missile defense has received additional funding as well. Statements by the U.S. government in 2004, however, imply that by 2012 the arsenal will drop to around 5,500 total warheads.