and it became the first permanently occupied mountain-top observatory in the world. Edward Singleton Holden was the first director. The location provided excellent viewing performance because of lack of ambient light and pollution; additionally, the night air at the top of Mt. Hamilton is extremely calm, and the mountain peak is normally above the level of the low cloud cover that is often seen in the San Jose area. When low cloud cover is present below the peak, light pollution is cut to almost nothing.