Marlboro Township is a township in Monmouth County , New Jersey , United States. The township is located within the Raritan Valley region and is a part of the New York Metropolitan Area . As of the 2010 United States Census , the township had a population of 40,191, reflecting an increase of 5,449 (+16.3%) from the 33,423 counted in the 2000 Census , which had in turn increased by 6,707 (+25.1%) from the 26,716 counted in the 1990 Census .

Marlboro Township was formed by an act of the New Jersey Legislature on February 17, 1848, from portions of Freehold Township .