Today in 1947, the Roswell Daily Record, a local paper in Roswell, New Mexico, published an article about a mysterious crash the previous day. And while you probably want me to hype this one up, I don't think the Roswell incident had any aliens. The best evidence that it was aliens is eyewitness accounts, and the first thing you learn in highschool forensics is that eye witness accounts are the weakest form of evidence because humans aren't built to remember things like that.
Also UFOs aren't even inherently aliens either. A lot of people always seem to default to any unidentified flying object being undeniable proof of aliens on earth. Aside from the mundane explanations for a majority of mystery objects, a UFO could be a time machine as easily as it could be an alien spacecraft. Or beings from a higher plane of existence. UFOs contain more possibilities than just aliens, and I think Roswell was the most likely the tail end of some US military thing they probably shouldn't have been doing in the first place.
[CONTRIBUTOR’S NOTE: The all-knowing Wikipedia.org says the Roswell debris was identified as a surveillance balloon from Operation Mogul. So hey! Right about it being a US military thing!]