Cheyenne Mountain

During the 20th century, the American military created a facility underneath Cheyenne Mountain, one mountain in a range of many on the western side of the United States. These ranges extended from Canada, far to the north past the United States border, down into the southeast of the country.

Before the Great War, Cheyenne Mountain Operations Center was host to four commands: North American Aerospace Defense Command (NORAD), United States Northern Command (USNORTHCOM), United States Strategic Command (USSACCOM), and Air Force Space Command (AFSPC).

Inconsistency
In Fallout Tactics, Mount Cheyenne became the hub of the Vault network; Vault 0.

However, in Van Buren, when the bombs fell, Cheyenne Mountain was a primary target. A huge section of the mountains became a great radioactive smoking crater, giving birth to a large population of glowing ghouls.

Clearly, the above versions are not consistant with each other, as there was no radiation around Vault 0 in Fallout Tactics. The Van Buren version seems more probable, as Cheyenne Mountain would be a likely target for a nuclear bomb.