Monroe Township is a township in southern Middlesex County, New Jersey, United States. It is an outer-ring suburb of New York City. As of the 2010 United States Census, the township's population was 39,132, reflecting an increase of 11,133 from the 27,999 counted in the 2000 Census, which had in turn increased by 5,744 from the 22,255 counted in the 1990 Census. Monroe Township was incorporated as a township by an act of the New Jersey Legislature on April 9, 1838, from portions of South Amboy T