This dataset contains version 2 of the Stream Classification for the Northern Appalachian – Acadian Region of Canada (New Brunswick, Nova Scotia, Prince Edward Island, and eastern Quebec) and cross-border watersheds of the United States (Maine, Vermont, New Hampshire, New York). Using a seamless base hydrography layer for the region, freshwater ecosystems were classified based on five biophysical characteristics: size, gradient, alkalinity, temperature, and tidal influence.