Space X Rocket Vapor

Last night I looked up and saw what looked like a comet racing out to sea. I was very curious about what it was until I saw the vapor trail from a rocket. I knew from seeing this sort of thing as a kid. I assumed it was a rocket launched from Vandenberg AFB, which it was.
Apparently people who have never seen such a thing thought it was a UFO. I was a little slow to get the camera and missed the rocket, but the trail it left behind was pretty cool looking. I think what this is a picture of is the point where the rocket went into the 2nd stage.