According to the United States Census Bureau, Washington borough had a total area of 1.945 square miles (5.039 km2),including 1.942 square miles (5.030 km2) of land and 0.003 square miles (0.009 km2) of water (0.18%) [REF].
Pohatcong Mountain is a ridge, approximately long, in the Appalachian Mountains that extends from west Phillipsburg northeast approximately to Washington.