At some point, Dillingham decided to throw his hat completely into the artistic ring, heading out to the region of the Pikes Peak Gold Rush, today's Colorado, and trying his hand at painting local scenes. He may have come with the intent of making sketches for eastern newspapers or magazines, though none are known to have been published. Dillingham traveled around the Front Range trying to sell his work to local businessmen and citizens. At some point he hooked up with John J. Pratt and Bela S. Buell, two local engineers and surveyors, who had been planning to issue a large map of the Colorado gold fields since late 1860.
Despite all the ways he tried to make money with his drawings-—by having them used as map illustrations, marketing the prints by subscription, selling naming rights, and getting commissions-—Dillingham does not appear to ultimately have been successful. The last we definitely hear of him is in April 1863, shortly after the Black Hawk print was published, when he announced he would be heading back “for a short trip East” in order to sell subscriptions. He isn’t mentioned again in Colorado, though appearing back in Chicago directories as an artist.