Although natives might complain about it, the Chicago Transit Authority runs the best metro rail service in the United States. Yes I know DC has a good one but it is a fraction of the size compared to Chicago. Chicago lines are usually on time, relatively clean,free of graffiti and also still moderately priced. This is a picture of an elevated train running parallel to the Chicago River. You can buy a print of this one and see other images on my commercial site by clicking here.