There are 500 Boeing-manufactured LGM-30 Minuteman III inter-continental ballistic missiles deployed in silos in the United States. Launch control crews are on alert around the clock with airborne crews ready to take over, should the ground-based crews be disabled.
Originally, the Minutemen were tipped with a single nuclear warhead, but they were the first ICBM's in the world to be MIRVed. Now, 300 of them carry three 335 kiloton warheads in independently-targeted reentry vehicles and the 200 remaining missiles carry three smaller 170 kiloton warheads.
Locations:
200 missiles - Malmstrom AFB, Montana
150 missiles - Minot AFB, North Dakota
150 missiles - F.E. Warren AFB, Wyoming
Some sources also list Grand Forks AFB, North Dakota, but USAF states the missiles have been moved to Malmstrom AFB.
The missiles are deployed in hardened silos at least 25 meters deep, with a shock isolated floor, debris collection system, EMP protection and blast hardening to 2000 psi.
Length: 60 feet
Weight: 79,432 pounds
Range: 6000-8000 miles depending on model
Speed: Mach 23
Accuracy (CEP): Less than 300 meters
Sources:
http://www.af.mil/news/factsheets/LGM_30_Minuteman_III.html
http://www.fas.org/nuke/guide/usa/icbm/lgm-30_3.htm
http://nuketesting.enviroweb.org/hew/Usa/Weapons/Mmiii.html