Is Denver Colorado the back-up capital of the US in the event something awful happens to Washington D.C.?

Answer 1

No.

I would say that the answer is "sort of". Denver has a significant Federal Government employment presence and the 2nd largest amount of Federal employees outside of DC. The question appears to ask about the Denver Federal Center in Lakewood, CO.

Building 710 is a 36,000 sf bunker designed to hold 300 people up to 30 days in the event of a nuclear attack. FEMA is now based there.

Building 810 was also a state of the art warehouse (in 1965). It contained all the supplies needed to service all government facilities for the General Services Administration (GSA).

So, Denver would likely be considered a repository during the Cold War "just in case", but it likely hasn't been really in the same status lately as it was in the 60's - 80's.

Answer 2

Growing up in Denver during the 60's and 70's, this was a common assumption and might even have been taught in our grade schools. However, no one knew at the time about the super secret alternate location buried beneath the Greenbrier Hotel in White Sulphur Springs, WV. That facility, created by order of President Harry Truman was (and still is) a marvel of advanced planning to house the entire government and their families in the event of a nuclear catastrophe. That facility is no longer a secret and may be a bit outdated for actual use today. So, how does Denver stack up now? In the age of global ballistic missiles it probably not as safe as one would imagine. However, it is centrally located and somewhat naturally protected by a huge mountain range to the west and an expansive prairie to the east. It's likely to survive a most of the fallout but, hey if that really ever happens, do we really care?