Henry D. Sokolski, Best of Intentions: America's Campaign Against Strategic Weapons Proliferation, 1945-2000 (Westport, CT: Praeger Books, 2001).
American administrations have struggled for over fifty years to control "the bomb." They have tried to limit the ability of the Soviet Union to destroy us with it; to keep other governments or private groups from getting it; to give us timely warning if those efforts should fail; and to reduce the likelihood of its inadvertent or deliberate use. All of this has involved dealing with states possessing vastly different degrees of power, whose relations with the United States ranged from close friendship to great hostility, and whose domestic politics varied greatly, from the stable to the mercurial and everything in between.
What can be said about the success of these efforts? There has been no military use of atomic weaponry since 1945, and there is but one notable exception--that by Iraq--to the non-use of chemical agents. As for the spread of the bomb, the number of countries that could make nuclear weapons today if they so desired (probably around fifty) is far greater than the number that actually has them (eight, or nine if North Korea has enough readily fissionable material). Similarly, the number of countries that possess rockets that can travel at least several hundred miles is much lower than the number capable of producing them.