Colorado

In the early 21st century, when the United States was divided into thirteen commonwealths, the old state of Colorado became part of the Four States Commonwealth, along with Utah, Arizona and New Mexico.

Of note for the Fallout universe, Colorado is home to NORAD and the Rocky Flats Nuclear Weapon Facility.

Military facilities in Colorado part of Rocky Mountains were saturated with nuclear bombs. In Fallout world there is a Crater.