White sucker, Catostomus commersonii, were collected from the St. Louis River Area of Concern in 2011, 2013, and 2015. The data include size, sex, and age of fish; associated orocutaneous and liver neoplasia prevalence; muscle carbon and nitrogen stable isotope ratios; diet contribution from three locations based on stable isotope ratios; and concentration of PCBs, dioxins, and furans in livers of select fish sampled in 2015. This dataset is associated with the following publication: Hoffman, J., V. Blazer, H. Walsh, C. Shaw, R. Braham, and P. Mazik. Influence of demographics, exposure, and habitat use in an urban, coastal river on tumor prevalence in a demersal fish. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, NETHERLANDS, 712: 12 pg., (2020).