Irwin and Madeline Caplan were married in 1948 when he returned to Seattle, where he teamed with illustrator Ted Rand and five other artists to form Graphic Studios, creating corporate logos and a variety of advertising artwork. In addition to such accounts as the Pacific Northwest Bell Telephone, Bardahl and the Mutual Life Insurance Company, Caplan also illustrated the 1962 Seattle World's Fair poster (sponsored by the Frederick & Nelson department store), plus work for the Seattle World's Fair Alaska Pavilion. He was the art director for Spokane's Expo '74.