The Minuteman III intercontinental ballistic missile (ICBM) is developed by the United States of America (USA). Here is a detailed explanation of this answer:

History and Background:
- The Minuteman missile program began in the late 1950s as a response to the growing threat of nuclear war during the Cold War era.
- The first Minuteman missile, Minuteman I, was deployed in 1962. It was followed by the improved Minuteman II in 1965 and eventually the Minuteman III in 1970.

Development and Features:
- The Minuteman III was developed by Boeing, an American aerospace company, under the guidance of the United States Air Force.
- It is an intercontinental ballistic missile, which means it is capable of delivering nuclear warheads over long distances.
- The missile has a range of approximately 13,000 kilometers (8,000 miles) and can travel at speeds of up to Mach 23 (around 17,500 miles per hour).
- It is a solid-fueled missile, which means it uses a solid propellant to generate thrust. This allows for a quicker launch time and greater reliability compared to liquid-fueled missiles.
- The Minuteman III is equipped with multiple independently targetable reentry vehicles (MIRVs), which means it can carry multiple warheads that can be aimed at different targets.
- It is also equipped with sophisticated guidance systems, including inertial navigation and global positioning systems, to ensure accuracy.

Operational Status:
- The Minuteman III has been the mainstay of the United States' land-based nuclear deterrent since its deployment in the early 1970s.
- The missile is housed in underground silos located across the United States, primarily in the states of Montana, North Dakota, and Wyoming.
- Over the years, the Minuteman III has undergone various upgrades and life-extension programs to ensure its reliability and effectiveness.
- As of today, the Minuteman III remains an integral part of the United States' strategic nuclear forces, although plans are underway to replace it with the Ground-Based Strategic Deterrent (GBSD) system in the coming years.

In conclusion, the Minuteman III intercontinental ballistic missile is developed by the United States of America. It is a vital component of the country's nuclear deterrence capability and has played a significant role in maintaining global security during the Cold War and beyond.