The oldest community in Washington Township, Grenloch Terrace, was a thriving Lenape Native American settlement called Tetamekon. In 2008, CNN and Money Magazine ranked Washington Township 58th on its list of the '100 Best Cities to Live in the United States'. The township is part of the Delaware Valley, also known as the Philadelphia metropolitan area, and the South Jersey region of the state. Washington, New Jersey, another borough, is surrounded by Washington Township in Warren County. It is one of five municipalities in the state of New Jersey with the name Washington Township. The township was named for George Washington, one of more than ten communities statewide named for the first president. Additional transfers to Gloucester Township were made in 19. Most of Washington Township, along with all of Monroe Township, was moved back into Gloucester County on February 28, 1871, with the remaining portions of Washington Township that were still in Camden County being transferred to Gloucester Township. Monroe Township was created on March 3, 1859, from part of the township. The township officially moved to the newly created Camden County on March 13, 1844.

Washington Township was incorporated by an act of the New Jersey Legislature on February 17, 1836, from portions of Deptford Township. For 2022, the Census Bureau's Population Estimates Program calculated a population of 49,234. As of the 2020 United States census, the township's population was 48,677, an increase of 118 (+0.2%) from the 2010 census count of 48,559, which in turn reflected an increase of 1,445 (3.1%) from the 47,114 counted in the 2000 census. Washington Township is a township in Gloucester County, in the U.S.

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