Barre is the most populous city in Washington County, Vermont, United States. As of the 2020 census, the municipal population was 8,491. P…Barre is the most populous city in Washington County, Vermont, United States. As of the 2020 census, the municipal population was 8,491. Popularly referred to as "Barre City", it is almost completely surrounded by "Barre Town", which is a separate municipality.