United States nuclear weapons
United States nuclear weapons fall into the categories of operational, in reserve, in decommissioning, historic, and research. Most weapons are allocated to the Single Integrated Operational Plan, but some are also allocated to the Unified Combatant Commands, especially United States European Command for NATO missions.
Nuclear weapon employment, for all practical purposes, can be authorized only by the civilian National Command Authority. There are some continuity of nuclear operations scenarios and command posts for what were primarily Cold War "decapitation" strategy.
The Obama Administration has announced policies of further restraint, essentially reserving their use against known nuclear powers, with possible exceptions for grave biological weapon threats from non-nuclear actors. On May 4, 2010, Secretary of State Hillary Clinton announced the U.S. has 5,113 nuclear weapons, a total that had been kept classified by all previous administrations. The high, in 1967, had been 31,255. 
- B61 tactical gravity bomb, delivered by tactical and strategic aircraft
- B83 strategic gravity bomb, delivered by strategic bombers (B-2 and B-52)
- W87 warhead for Minuteman land-based ICBMs
- W88 warhead for Trident II submarine-launched ballistic missile
- W80 air-launched cruise missile warhead
Some weapons in the stockpile are the same as in active use, but are spares to replace operational ones that need maintenance. In addition, there are weapons that could be returned to operations.
Nuclear weapons infrastructure
There are two design centers for nuclear weapons, Los Alamos National Laboratory in New Mexico and Lawrence Livermore National Laboratory in California; both do a range of nuclear engineering and basic research.
The major overhaul facility is the government-owned, contractor-operated Pantex Plant in Amarillo, Texas.
- Mary Beth Sheridan and Colum Lynch (4 May 2010), "Obama administration discloses size of U.S. nuclear arsenal", Washington Post