Gray's first pieces, headland seascapes, were exhibited in 1907; soon thereafter he addressed in watercolor eucalyptus groves and fields of California wildflowers. These subjects would become signatures of his work. Originally Gray's works were oils; however, he eventually developed an allergy to oil paints, and therefore switched to using watercolors as his primary medium.
Having been a bachelor for 53 years, Gray surprised his friends by marrying. He and his bride moved to the Bonificio Adobe in Monterey, where seascapes and cypress dominated his later works.
In 1939 the Grays sold their adobe and moved to San Francisco. Restless for the out of doors, Gray and his wife moved to San Anselemo at the base of Mount Talapais in 1941. After ten years in Marin County, his wife died and he returned to San Francisco. Gray died on October 10, 1952 from a heart attack.