In 1859 Bush married a widow, Mandana Kimsey, and established a farm 12 miles south of the family homestead. The couple had three children, George O., John Shotwell, and Mandana Isabella. George O. Bush died in infancy. After his father's death, William Owen Bush took control of the family farm, operating it together with his brothers and growing the family into increasing prosperity and wealth. In 1872 Bush helped found the Western Washington Industrial Association, which organized agricultural expositions, serving as the group's inaugural president. Grains from the Bush farm won gold medals at the 1876 Philadelphia World's Fair, and the 1893 Chicago World's Fair. In 1893 he was appointed to represent the United States on the Advisory Council of the World's Congress Auxiliary on Farm Culture and Cereal Industry.