It’s all a big miscommunication. The government says there is no Area 51 and then the whackos say, “Yeah there is, I can see it from this hill.” But the government couldn’t just come out and say, “Oh no, that’s a super secret test facility, Area 51 was really just an arbitrary division of government land. That area name isn’t used anymore.” So they just kept repeating the truth, “There is no Area 51.” And the whackos just kept on, not listening.
In the early 1950s the Atomic Energy Commission, realizing that a need existed for an area to test the yield and capacity of their new and future nuclear warheads, petitioned for an area to use as a testing ground. They wanted someplace they could blow up and not worry about the repercussions. Previous to 1950 they had been performing these tests on islands in the Pacific ocean. That practice had become costly and some felt there was a security risk to performing the tests outside the national boundaries of the United States. So, on 11 Jan 1951, President Harry Truman created what was then known as the Nevada Proving Grounds, in a remote portion of the state of Nevada. The site was nearly a hundred miles from any sizable population center and the land was all government owned. The AEC divided the site into different "Areas" one of these areas was Area 51.
In 1955 NPG changed hands to the Department of Energy and was renamed the Nevada Test Site. At that time several of the former NPG areas were reallocated to other organizations including the US Air Force. The Air Force then sub allocated their chunk out to the likes of Nellis AFB for use as a gunnery and bombing range and they even kept a little bit for themselves to use as a secure site for the development of secret aircraft.
One of the areas released by the DOE to the Air Force was Area 51. The previously super secret Groom Lake Air Base sits in a portion of what used to be called Area 51. Area 51 no longer exists and hasn't for a good number of years.
However, there is a giant piece of land used for a number of secret and not so secret projects. For years the Groom Lake facility, or dreamland to some, was the site of research and development of such aircraft as the U2, SR-71 and the F-117 among others. The largest function of the NTS was the detonation of several thousand nuclear warheads of varying yield. Those tests continued until the current moratorium began in 1992. Many other conventional weapons systems were tested on the Nellis Range as well.
So, even if there was no Super Secret Government Conspiracy To Hide Aliens at the NTS, there were a number of really good mundane reasons to keep people out. Even though they no longer test nuclear devices at the NTS there are many areas that are still very radioactive. A number of structures were constructed or relocated by the NTS to test their resilience to the forces of nuclear explosions. They built an entire town and blew it up. They constructed heavy steel launch platforms and other ugly structures. They even moved in a Naval destroyer or two. All of these things are now impossible to move and represent a clear danger to snoopy whackos looking for monsters.
The most heavily guarded area and the source for the most consternation was the Groom Lake facility. This facility was used to build some of our most secret and advanced aircraft. It was an area of extremely sensitive national security. Consequently security was very tight and provisioned to take precautions that may have seemed extraordinary.
A good friend of mine's father was in Air Force Security for many years. He recently began recounting stories from his time while stationed at Nellis in the early eighties. He was part of a force that provided on-site ground security for the F-117 during its development and flight tests out of the Tonopah facility. He recalled to me one time that when they caught someone inside the facility boundaries they handcuffed and blindfolded the trespasser and held them for 48 hours without explanation. After this time was up they confiscated everything except the trespassers clothes and vehicle and released them, all without speaking to them or answering a single question. He explained to me that they had really been quite easy on these folks as they were authorized to use deadly force.
Military security forces are not bound by the same legislation that police officers are. In the case of national defense the military will often go to extreme measures to protect what they feel could provide extreme harm in the hands of an enemy. High security military areas are always well labeled and the use of deadly force is well posted. You may not see anyone at the fence, but if you cross it, you were warned. I have seen people arrested and detained without trial for simply attempting to cross the rope boundary around a B-1 bomber at an air show.
There is no Area 51, but the US government does have secrets, some good and some bad, that they don’t want to tell you about. Sometimes they keep people out for their own protection. Sometimes, when they say a thing doesn’t exist, they’re telling the truth and you just don’t want to hear it.