Born in Bath, Maine, William Prior became an itinerant portrait and landscape painter who also painted on glass. In 1841, he settled in Boston after traveling and painting widely for ten years around New England. In Boston, he established a portrait studio with his brother-in-law, Sturtevant Hamblin, and he stayed there until 1846, when he moved to East Boston. He is best known for his naive "flat" work, especially full-length child portraits with vibrant colors and little detail on hands and feet. He differed from many contemporary portrait painters in that he placed his subjects against a soft, atmospheric background rather than one of bright color.