i just had to do a research paper on area 51. they did move the location to some wheres near the four corners of Colorado, Utah, Arizona, and New Mexico because of a couple reasons.
one was some shit about an open skies treaty the US has w/ other countries where we can fly over each others territories or something, so they moved to keep it as secret as possible because of how everyone knew where it was.
another reason was because the elevation, it was ideal for some kind of new "pop up missile" so the higher the elevation the further the missile missions could travel.
sry for the novel but thats what i got out of researching it last month