For about two years, from 1969 to 1971, he was vice president for research at the Coe Kerr Gallery in New York.
In 1971, he joined the faculty of Brooklyn College as a professor of art history, an appointment transferred to the Ph.D.
[4] He became professor emeritus on his official retirement in 1999; he continued to teach at Hunter College, CUNY, for several more years.
[6][7] His years of collecting began with nineteenth-century American still life pictures while in Newark.
[3] Following his retirement, Gerdts continued to represent a deeply conservative type of white male-dominated American art history founded in connoisseurship.