Home-based businesses represent a large and growing portion of the economy, though little is known beyond limited surveys. This paper describes a novel method of identifying businesses located within residences using parcel-level land use data across 15 counties in California and analyzes their evolution from 1997 to 2014, focusing on their distribution across neighborhoods. Home-based business represented nearly one in six businesses in 2014, and employment in home-based businesses outpaced overall employment growth 37 to 24% from 1997 to 2014. While home-based businesses are associated with both middle-income and wealthy neighborhoods, only in southern California were they associated with growing shares of single-family housing, low population density, and homeownership rates. While prior research emphasizes the importance of technologically and knowledge-intensive services across a variety of home working arrangements, this study reveals that the industrial composition of home-based businesses is roughly equally comprised of knowledge-intensive services and basic economic activity.