His first jobs were brochures for the National Crayon Company and illustrations for the Boston Herald. His career took off when the New York World sent him to Cuba, where, in the days before news photography became commonplace, he became a sketch artist for important events. He rose to become the art editor for The World.
In 1908, Dart produced his comic strip The Explorigator.
The strip ran for 14 weeks in 1908. Dart went on to become a prolific cartoonist, continuing with Boys Will Be Boys in 1909 and Life and Judge in the 1920s.
He died in Laconia, New Hampshire, in 1938.