This data release contains the results from a study that characterized the concentration and quality of dissolved organic carbon (DOC) in the McKenzie River, a relatively pristine watershed in western Oregon, and its link to forming disinfection by-products (DBPs) in treated drinking water. The study aimed to identify the primary source(s) of DOC in source water for the Eugene Water and Electric Board’s (EWEB) conventional treatment plant on the McKenzie River near river mile 11, upstream of Hayden Bridge. The two classes of regulated compounds examined—trihalomethanes (THMs) and haloacetic acids (HAAs)—form when organic carbon in raw source water reacts with chlorine and (or) bromine during water treatment. The data release includes six general types of data: 1) the concentration of dissolved organic carbon in filtered water samples; 2) the concentration of disinfection by-products (DBPs) in finished (treated) drinking water; 3) raw absorbance data for filtered water samples; 4) fluorescence excitation-emission matrices in vectorized format; 5) Parallel factor analysis (PARAFAC) component loadings for the fluorescence excitation-emission matrices; and 6) the percentages of different land cover for the watersheds draining to the sampled sites.