In the Sheepscot River, ME, we measured percent saturations of dissolved methane (CH₄) and carbon dioxide (CO₂) and concentrations of nitrate (NO₃^-) four times in the main stem and once in the West Branch. River water was super-saturated with CH₄ at all sites throughout the study, and measurements were generally higher at lower-gradient sites (1000–5000% saturation) than higher-gradient sites (generally <1000%). Percent saturations of CO₂ in the main stem varied in both time and space and were under-saturated at some sites. CO₂ percent saturations and NO₃^- concentrations in the more-developed West Branch were significantly higher than the main stem, likely because of the position of mainstem sites downstream of Sheepscot Pond where primary production and degassing could occur. We also measured CH₄ and CO₂ fluxes from wetland soil adjacent to the main stem, which averaged 710 (± 59) µmolCH₄/m²/h and -51 (± 6.4) mmolCO₂/m²/h. Our findings suggest that rivers and fringing wetlands in the formerly glaciated northeastern US contribute to the production of greenhouse gasses, and that dissolved methane shows spatial variations with channel morphology.