Erie is a city in and the county seat of Neosho County, Kansas, United States, and situated in the valley of the Neosho River, about a mile N…Erie is a city in and the county seat of Neosho County, Kansas, United States, and situated in the valley of the Neosho River, about a mile Northeast of the river. As of the 2020 census, the population of the city was 1,047.