The US military has plenty of good reasons to keep its operations away from the general public. However, they've been known to make mistakes in the past, letting slip the dark side of their work and botching attempts to cover it up. In some cases, there is hard evidence that reveals horrifying secrets; in others, the public has used tidbits of leaked information to piece together theories.
Check out some of the areas and operations conducted by the US military that should have stayed a secret, and the conspiracy theories that many Americans believe.