While New Jersey was an English colony, Mendham Township was formed as a township on March 29, 1749, from portions of Hanover Township, Morris Township, and Rockaway Township. After the American War of Independence, the township was incorporated under the same name by an Act of the New Jersey Legislature on February 21, 1798. Portions of the township were taken to create Randolph Township on January 1, 1806. The village of Mendham, adopted the newly created borough form of government on May 15, 1906 and withdrew from the governance of the township council.
