From the auction site for the piece:

Daniel E. Greene (born 1934) is an American artist who works in the media of pastels and oil painting. The Encyclopædia Britannica considers Mr. Greene the foremost pastelist in the United States. To date, Daniel Greene has painted over 117 works depicting scenes of the New York subways, which he describes as a source of constant inspiration. His 2004 exhibition SUBWAY PAINTING at the New York Transit Museum at Grand Central Terminal was the inaugural event in the centennial year of the New York City Subway. Through his paintings of people riding in or waiting for the subway, seemingly mundane occurrences, Greene reveals his affinity for conveying his unique perception of the ordinary.