He earned a master's degree in fine arts from the University of Pennsylvania where he also used to study architecture.
When World War II began he joined the U.S. Army Camouflage Corps.
Later on, he married Frances Lubanda, a United States Weather Bureau worker.
During his History of Art class, he made a point of showing his students the difficulties which Michelangelo had when he was painting the Sistine Chapel: Professor Hartgen would lie down on the table at the front of the classroom and hold a clipboard just inches away from his nose.
[2] As a collector he collected 5,000 art pieces which were painted by such famous artists as Berenice Abbott, Jasper Johns, John Marin, Diego Rivera, Giovanni Piranesi, Käthe Kollwitz, and Andrew Wyeth.