Iron Mountain is mentioned in Fallout 2, but does not actually appear in any game.
Behind the scenesEdit
There are several such Iron Mountains in the United States; one is a short 9 mile walk to the northwest of Redding, fairly close to Arroyo and Navarro. Another Iron Mountain, located in Utah, is a part of NORAD along with Cheyenne Mountain. However, it is most likely that the location is a reference to the Report from Iron Mountain satirical book.