ISP Alginates (formerly Kelco Co.) has collected information on the abundance of giant kelp (Macrocystis pyrifera) in California and Mexico from routine aerial surveys since 1957. The standard protocol consists of an observer visually estimating the amount of harvestable giant kelp biomass within designated kelp beds from a small fixed-wing aircraft. Observations were recorded on paper data sheets in the field and archived in notebooks housed at ISP Alginates. With cooperation from ISP Alginates, the SBCLTER converted ISP Alginates long-term records of giant kelp biomass into a digital format. The database consists of a data table containing kelp biomass, a catalog of maps. The format ISP Alginates used to report kelp abundance data changed periodically over the course of the collecting period. These details, pus descriptions of designated kelp beds are described in the protocol document.