Illustration artists must be versatile and adaptable as their commissions can cross genres from one assignment to the next -- from cowboys to pirates, peasants to kings, enemies to lovers, from historical to contemporary to the fantastic. A commercial assignment for an advertisement is therefore not materially different from one for a story, so it is not surprising that James E. Allen was tapped for advertising commissions.
What was unusual was how two advertising series in particular helped establish Allen's name to a much broader audience, as a popular illustrator of dinosaurs and a serious artist of the industrial world. The Sinclair Dinosaur book was an advertising give-away associated with Sinclair Oil's popular exhibition of animatronic dinosaurs at the Chicago World's Fair. Through this publication and subsequent stamp albums, Allen's dinosaurs were seen by millions. Lithographs of a pipe workers for the U. S. Cast Iron Pipe and Foundry company were editioned and displayed as fine art in a New York Gallery, a likely cross-over first for commercial art.