Gregor Duncan arrived in New York City in 1933, and began working for the old Life magazine as an editorial cartoonist in the same year. His cartoons reflected the magazine's political outlook, from initial support of FDR's New Deal, to a later opposition of what the publication perceived as FDR's bloated bureaucracy. Duncan continued working for Life until the magazine ceased publication in November 1936.
While working for Life, Duncan cultivated other clients in the magazine business during his short time in New York. He he had cartoon and illustration work appearing in Reader's Digest, Collier's Weekly, and Cosmopolitan. Duncan also drew and painted covers for the Literary Digest, Judge, and For Men Only.
Duncan was also active in the newspaper field, drawing features for PM, the left-wing daily published by Ralph Ingersoll, from its inception in 1940. Duncan acted as a journalist-illustrator for PM, covering all sorts of topics and events throughout the city. A lifelong left-winger, Duncan also contributed work to the Communist Party's Daily Worker, but signed those pieces with the pseduonym "George Dickson", which was a variation of his mother's maiden name of Dixon.
During his time in the Army Air Force, Duncan contributed writing and illustrations to both PM and LOOK magazine, in an ongoing effort to keep the public informed.