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). Throughout the Cold War, Cheyenne Mountain was considered a primary target in all first-strike and second-strike scenarios. Although the mountain was designed to withstand multiple direct hits from nuclear weapons, projections were universally pessimistic as to the survival of the installation.

According to Fallout 2 NORAD computer stations were offline (at least in 2241 when checked by Chosen One from Poseidon Oil Powerplant No 12). Whether this represents a communications interruption or the wholesale destruction of NORAD is never made explicitly clear, but given the target status of NORAD it is highly likely that the facility was at unoperable status.

Inconsistency
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. Coupled with attacks on Denver and the Rocky Mountain Arsenal, Boulder became the center of a triangle of hellish death.

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

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.