Portions of the township were taken to form Chambersburg on April 1, 1872, and annexed by Trenton in 1888, and by Wilbur on April 24, 1891, and annexed by Trenton in 1898.

Hamilton was incorporated as a township by an act of the New Jersey Legislature on April 11, 1842, from portions of the now-defunct Nottingham Township. The township was the state's ninth-largest municipality in 20, after having been ranked 10th in 2000. As of the 2020 United States census, the township's population was 92,297, its highest decennial count ever and an increase of 3,833 (+4.3%) from the 2010 census count of 88,464, which in turn reflected an increase of 1,355 (+1.6%) from the 2000 census count of 87,109. The township is situated within the New York metropolitan area as defined by the United States Census Bureau but directly borders the Philadelphia metropolitan area and is part of the Federal Communications Commission's Philadelphia Designated Market Area.

It is the largest suburb of Trenton, the state's capital, which is located to the township's west. Hamilton Township is a township and the most populous municipality in Mercer County, in the U.S.

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