Mansfield Township is a township in Warren County, in the U.S. state of New Jersey. As of the 2020 United States census, the township's population was 7,781, its highest decennial census count ever,
What is now Mansfield Township was formed on May 30, 1754, as Mansfield-Woodhouse Township from portions of Greenwich Township, while the area was still part of Sussex County, and was incorporated as Mansfield Township on February 21, 1798, as one of New Jersey's initial group of 104 townships by an act of the New Jersey Legislature. The township became part of the newly formed Warren County on November 20, 1824. Portions of the township were taken to form Franklin Township (April 8, 1839) and Washington Township (April 9, 1849). The township was named after William Murray, 1st Earl of Mansfield.
Geography
According to the United States Census Bureau, the township had a total area of 29.69 square miles (76.90 km<sup>2</sup>), including 29.59 square miles (76.63 km<sup>2</sup>) of land and 0.11 square miles (0.27 km<sup>2</sup>) of water (0.35%).
Other unincorporated communities, localities and place names located partially or completely within the township include Karrsville, Mount Bethel, Penwell, Rockport and Stephensburg.
The township borders the municipalities of Hackettstown, Independence Township, Liberty Township, Oxford Township and Washington Township in Warren County; Lebanon Township in Hunterdon County; and Washington Township in Morris County.