Coolidge began his art career in his twenties, one of his early jobs being the creation of cartoons for a local newspaper. And he absolutely fell in love making art. And wanted to make his own. Above is some of his cartoons he did with the newspaper.
According to the advertising firm Brown & Bigelow, then primarily a producer of advertising calendars, Coolidge began his relationship with the firm in 1903. From the mid-1900s to the mid-1910s, Coolidge created a series of sixteen oil paintings for them, all of which featured anthropomorphic dogs, including nine paintings of Dogs Playing Poker, a motif that Coolidge is credited with inventing.
He is credited with creating "comic foregrounds," novelty photographs which combined a portrait of the sitter with a skit (dog) body, produced by the sitter holding between two sticks a canvas on which Coolidge drew or painted dogs. The final product was similar to the photographs produced using photo stand-ins at midways and carnivals where people place their heads into openings in life-size animals.