This data set includes 28 physical watershed attributes for each of 135,118 stream segments (National Hydrodraphy Dataset, Version 1) in California. These data were used to support a report entitled: "Classification of California streams using combined deductive and inductive approaches: setting the foundation for analysis of hydrologic alteration" authored by Pyne, Carlisle, Konrad, and Stein, and published in the journal Ecohydrology. Specifically, these data were used in a classification (ie, cluster) analysis to identify unique groupings of watersheds with similar hydrological characteristics.