A water-powered grist mill was built in 1819, about half a mile from the church. In 1821, a fulling mill was added, designed by newly arrived American immigrant Joseph John Chapman. He oversaw the building of a grist mill for Mission San Gabriel, and he prepared timbers for the construction of the first church in Los Angeles. The mill he built near San Gabriel is now a museum. Chapman was baptized at San Buenaventura in 1822, and that same year married Guadalupe Ortega of Santa Barbara, with whom he had five children. In 1824, Chapman bought land in Los Angeles and developed a vineyard, but still continued to perform odd jobs at the missions.