Born in Québec City, he moved with his family to Montreal in 1869, where he apprenticed for an engraving firm. Commissioner George Arthur French of the North-West Mounted Police appreciated the value of good public relations. He knew the Canadian public was interested in the new police force and thought that providing a visual record of the force would help maintain that interest. Since in 1873 photographs could not be reproduced in newspapers, French wrote to the manager of the Canadian Illustrated News inviting them to send an artist-journalist to accompany the expedition. The idea appealed to the newspaper as they would get an exclusive set of articles and pictures to publish. The young artist was immediately sent on his way.
Nevertheless, Julien's western experience gave him a degree of self-assurance he had not previously possessed, and it was not long before he became a leading figure in the field of illustrative art in Canada. The 1870s and 1880s were the heyday of the engraver and lithographer, just before the machine replaced the artist, and Julien's illustrations were sought by magazines around the world. He is buried in Montreal's Notre Dame des Neiges Cemetery. His drawing Le Vieux de '37, depicting an old man going to fight the Lower Canada Rebellion, is one of his best known of his works and of the Patriote iconography today.