is a borough in Warren County, New Jersey, United States. As of the United States 2000 Census, the borough population was 6,712. The borough is located in the eastern most region of the Lehigh Valley.
Washington was incorporated as a borough by an Act of the New Jersey Legislature on February 20, 1868, from portions of Washington Township.
According to the United States Census Bureau, the borough has a total area of 2.0 square miles (5.1 km
Pohatcong Mountain is a ridge, approximately 6 mi (10 km) long, in the Appalachian Mountains that extends from west Phillipsburg northeast approximately to Washington. Upper Pohatcong Mountain extends northeast of Washington approximately 6 mi (10 km) to the vicinity of Hackettstown. The two ridges are sometimes called "Pohatcong Mountain" collectively.