The LGM-118A Peacekeeper was a land-based ICBM deployed by the United States starting in 1986. Under the START II treaty, which never entered into force, the missile was to be removed from the US nuclear arsenal in 2005, leaving the LGM-30 Minuteman as the only type of land-based ICBM in the US arsenal. In spite of the demise of START II, the last of the LGM-118A "Peacekeeper" ICBMs were decommissioned on 19 September 2005.

The Peacekeeper was a MIRVed missile: each rocket could carry up to 10 re-entry vehicles armed with a 300-kiloton W87 warhead/MK-21 RVs (each twenty-five times the power of the bomb dropped on Hiroshima during World War II).

Reagan pushed the name Peacekeeper, but the missile was officially designated the LGM-118A. It was first test fired on June 17, 1983, from Vandenberg AFB, California, traveling 4,200 nautical miles (7,800 km) to impact successfully in the Kwajalein Test Range in the Pacific. The operational missile was first manufactured in February 1984 and deployed in December 1986 to the Strategic Air Command, 90th Strategic Missile Wing at F.E. Warren AFB in Wyoming into retro-fitted Minuteman silos. Fifty working missiles had been deployed at Warren by December 1988. The planned deployment of one hundred missiles was canceled by Congress in July 1985, again over the survivability issue. In that decision, Congress limited the deployment Peacekeeper ICBMs to 50 missiles until a more survivable basing plan could be developed.

The survivability issue was to be solved by a "rail garrison" system whereby 25 trains, each with two missiles, would use the national railroad system to conceal themselves. It was intended that this system would become operational in late 1992, but budgetary constraints and the changing international situation led to it being scrapped.

The project has cost around $20 billion (up to 1998) and produced 114 missiles, at $400 m for each operational missile. The "flyaway" cost of each missile is estimated at $20–70 million.

The missiles were gradually retired, with 17 withdrawn during 2003, leaving 29 missiles on alert at the beginning of 2004. At the start of 2005 only 10 remained on alert, scheduled to be retired by the end of the year. The last Peacekeeper was removed from alert on 19 September 2005 during the final deactivation ceremony when the 400th Missile Squadron inactivated as well.

Hey, anyone hear Iran's soon gonna go nuclear? At least they're a peaceful, tolerant nation with no enemies....