The Robert H. Sunday House in Marshalltown, Iowa, is a Frank Lloyd Wright-designed Usonian residence from his later career and one of his Iowa houses. After an initial Usonian Automatic concrete-block plan proved unworkable, Wright produced the brick design that was built, closely related to his 1953 Usonian Exhibition House. It was the sixth of seven Iowa houses he designed and built in this style and is believed to be the last such example built in brick. Robert H. Sunday, owner of Marshall Lumber, served as general contractor, and he and his wife completed much of the work themselves. A 1970 addition by Wright assistant John H. “Jack” Howe changed the plan from L-shaped to T-shaped.