It was named after the Harring family, who were early settlers to the region by 1633.
[3] The passage of a revised Borough Act resulted in the "Boroughitis"-inspired subdivision of the township into new municipalities: Delford (now Oradell) on March 8, 1894; Eastwood (part, borough lasted until 1896 to become part of Old Tappan) on June 6, 1894; Schraalenburgh (now Dumont) on July 20, 1894; and Old Tappan on October 8, 1894.
Portions of Harrington Township were taken on April 8, 1903, to form parts of both Demarest and Alpine.
The final wave of departures saw the creation of Closter (January 1, 1904), Haworth (February 24, 1904), Harrington Park (March 29, 1904) and Norwood (March 14, 1905).
[3] On March 15, 1916, the remainder of Harrington Township became Northvale.