Plattsburgh is a city in and the county seat of Clinton County, New York, United States, situated on the north-western shore of Lake Champlain. The population was 19,841 at the 2020 census. The population of the surrounding Town of Plattsburgh was 11,886 as of the 2020 census, making the combined population of Plattsburgh to be 31,727. Plattsburgh lies just to the northeast of Adirondack Park, immediately outside of the park boundaries.