Yes, it was a Cold War site. There for testing and messing around with all the stuff the military enjoys messing around with. Nearby, Nellis AFB is the home of not only the Blue Angels, but a whole lot more jet fighters. And about 35 miles further out toward Area 51, the Air Defense Command operated a radar site until 1967. Some of those stationed on the site required crypto clearance to do so. And what were they watching? Anything down below! (If you caught anything Soviet already that far inland, you were already well and truly screwed anyway.) Twice each day, the fighters upstairs would break the sound barrier, and teacher in the elementary school would automatically shutup a split second beforehand. Hide from the nukes under you desks drilled occurred monthly, and local civilians built bomb shelters - not anti-alien survival pods.
AFAIK, all the little green guys were limited to Roswell, NM, which was home to Walker AFB until it was also shuttered in 1967. There is plenty people assigned to those bases won't talk about - but their security clearances required that no matter what.
The interesting thing is, these bases were supposedly closed to free up more money for the VN WAR, but these locations housed military geeks - particularly, Angel's Peak. The technology employed there was NOT outdated in 1967, and personnel were simply transferred to other sites which employed the same equipment and skills, but watched other potential countries/groups. Like Castro, for example. There were nearly identical operations in Florida. That says that the tech wasn't dead, only the potential targets and products being tested had changed.
And given that the US military has just about nothing to say as to when aliens can be declared antiquated or irrelevant, you really do have to roll with the way their actions speak to us. Nobody was talking aliens outside of the latest Star Trek episode, and then EVERYBODY was talking aliens. And if there WERE actual aliens, would somebody explain to me why all those guys were still reading sci-fi on the way to and from and sharing their books? Because, that, of all things would simply not happen, if they had any thought of real aliens on the desert floor below.