Montague Township is a township in Sussex County, New Jersey, United States. As of the 2010 United States Census, the township's population was 3,847, reflecting an increase of 435 (+12.7%) from the 3,412 counted in the 2000 Census, which had in turn increased by 580 (+20.5%) from the 2,832 counted in the 1990 Census. Montague Township was supposedly named after the George Montagu, 4th Duke of Manchester, as suggested by King George II, who approved the royal patent on March 26, 1759. Montague was incorporated on February 21, 1798, as one of New Jersey's initial group of 104 townships by an Act of the New Jersey Legislature. Before Montague Township was granted its own post office in the 1980s, residents had all of their mail delivered through the 12271 ZIP code for Port Jervis, New York, leading to situations where residents had New Jersey driver's licenses with a New York State address.