This dataset identifies the number of individually-owned domestic wells, and the number of households relying upon domestic water supply in the state of California. The number of wells and households are summarized for each Public Land Survey System (PLSS) section. The well locations were determined from more than 635,000 scanned well-completion reports (WCRs) provided by the California Department of Water Resources in 2011. This is only a partial sample of the total number of WCRs (estimated at 1 to 2 million in total). The number of domestic wells was estimated based upon a spatially distributed and randomized survey that determined the Township Ratio (TR) for each township in the state (4,692 in total). Each township generally contains 36 sections (6 x 6). The total number of wells within a section was multiplied by the corresponding TR to estimate the number of domestic wells within each section. See the "TRatio" column in the attribute table. Each section within the same township will have the same Township Ratio. The domestic household data are from the 1990 US Census. These data were provided at the census tract level and were subsequently aggregated to PLSS sections that contained a domestic well. In the case where census tract data identified households using domestic supply, but there were no domestic wells within the tract, the household data were distributed evenly to all sections within the tract. In San Luis Obispo County, the scanned WCRs were incomplete. Therefore, a surrogate method was used. The total number of households reported by the 1990 census did not change; only the distribution of where those households existed within the tract changed. A WCR was considered an individually-owned domestic well if the primary use of the well was identified as being domestic, the owner was an individual, and the well was not destroyed as of 1990. See the larger body work (Johnson and Belitz 2015) for more details.