A cold front came from the North and, despite a high-pressure ridge, air in Estes Park and in the eastern portion of Rocky Mountain National Park was unusually clean. I and my camera visited the same vantage points from which we had documented high levels of particulates, haze, and smog. The clean-air images enable comparisons of image quality and air quality - on dirty-air days and clean-air days. Circa 2009, clean air days in Estes Park and in the eastern portion of Rocky Mountain National Park occur very rarely.