Reinhardt joined the staff of PM in 1942 and he worked full-time at this daily newspaper until 1947, with time out while drafted for active duty in the U.S. Navy. While at PM he produced several thousand cartoons and illustrations most notably the series of famous and widely reproduced How to Look at Art series. Reinhardt also illustrated the highly influential and controversial pamphlet Races of Mankind (1943) originally intended for distribution to the U.S. Army, but after being banned subsequently sold close to a million copies. He also illustrated a children's book A Good Man and His Good Wife. While attending Columbia University he designed many covers and illustrations for the humor magazine Jester and was its Editor in his senior year (1934–35). In 1940 he was the designer of "The Chelsea Document", a public exhibition of five 4x8 foot panels.Other commercial art work was done "for such varied employers as the Brooklyn Dodgers, Glamour magazine, the CIO, Macy's, The New York Times, the National Council of American-Soviet Friendship, The Book and Magazine Guild, the American Jewish Labor Council, New Masses, the Saturday Evening Post, Ice Cream World, and Listen magazine. He illustrated many books such as Who's Who in the Zoo.