It was designed to replace the Minuteman III, being the first "third-generation" ICBM. Design work began in 1972 on the MX (Missile-eXperimental). Apart from technical improvements in the missile the issues of survivability and mobility were regarded as of increasing importance. In 1976 Congress refused to fund a silo-based system on the grounds of vulnerability and the project was halted until 1979 when President Carter approved the missile development and a system of multiple protective shelters linked by rail as a deployment system. President Reagan cancelled the new shelter system in 1981 and pushed for a "dense pack" solution to speed deployment in 1982, Congress again rejected the silo based sytem. A compromise was developed in mid-1983, by which there would be swift deployment of 100 new missiles in silos to show "national will" and remove the Titan II ICBM from use followed by a new more mobile single-warhead ICBM later.
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, it covered 6,700 km to impact successfully in the Kwajalein Test Range in the Pacific. The operational missile was manufactured from February 1984 and first deployed in December 1986 to the 90th Strategic Missile Wing at F.E. Warren AFB in Wyoming to retro-fitted Minuteman silos. Fifty working missiles had been deployed at Warren by December 1988. The planned deployment of a hundred missiles was cancelled by Congress in 1985 again over the survivability issue.
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 to begin this system 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 only $20-70 million.
LGM-118A Peacekeeper