Monroe Township is a township located in southern Middlesex County, in the U.S. state of New Jersey. The township is centrally located within the Raritan Valley region and is an outer-ring suburb of New York City within the New York metropolitan area. As of the 2020 United States census, the township's population was 48,594, its highest decennial count ever a…Monroe Township is a township located in southern Middlesex County, in the U.S. state of New Jersey. The township is centrally located within the Raritan Valley region and is an outer-ring suburb of New York City within the New York metropolitan area. As of the 2020 United States census, the township's population was 48,594, its highest decennial count ever and an increase of 9,462 from the 39,132 recorded at the 2010 census, which in turn reflected an increase of 11,133 from the 27,999 counted in the 2000 census. Monroe Township also comprises the largest land area of any municipality in Middlesex County, at approximately 42 square miles.