William Hannum's interest in surfing, painting, and drawing began in childhood. He habitually carried a sketchbook to capture regional scenery and record notes about color and mood. His formal training included studies at the Otis Art Institute in Los Angeles and the Art Students League in New York City. Although his paintings appear to be created on location, Hannum was a studio painter, building on ideas from his sketches and progressively working them into a complete theme. Hannum's painting style was influenced by two Carmel Art Association artists: The late George DeGroat, and Keith Lindberg. Hannum was one of the most popular Artist Members ever represented by the Carmel Art Association. His paintings commonly depicted rolling California hillsides, coastal scenes, trees, and still life subjects. Bold, broad brush strokes executed with thick, intense color characterized his expressionist style. Hannum created works of art that intentionally conveyed a feeling of robust vitality. Through these gestural strokes he expressed his emotional response to nature or an image. His work was highly sought after throughout his fourteen-year association with the CAA, and it has been ever since until his untimely death from cancer at age 51 in 1998.