I arrived at the youth camp, outside Rapid City SD around 11:30 pm. I had been working there as a night supervisor, making sure the youths didn't leave the camp. Just as I pulled into camp the ufo glided over the treetops and the building. It stayed there for some time, bringing other workers out of the building, to see what it was, then glided away. There was no sound, just the blinking light on the bottom. Later, threw the time I worked there, I noticed children would stagger back into to the buildings, acting like the were drunk. Looking back, I wish I would have checked into the matter better. Note: Years after, I always had a feeling of being under observation. I am sorry about the insufficient data, but this took place in 1973, there wasn't much for multimedia forms back then, This facility was run by the government. I am reporting this now because I wanted someone to know, without thinking I was making it up. I don't remember the people I worked with. Quit shortly after the sighting.