Warren was originally inhabited by the Lenape Native Americans and was colonized in the 1720s by European farmers. As early as 1900, it became a destination for wealthy residents looking to escape nearby New York City. Warren was incorporated as a township by an act of the New Jersey Legislature on March 5, 1806 from portions of Bernards Township and Bridgewater Township. The south-eastern half of the original township (which was close to a railroad and contained most of the population) was separated off as North Plainfield Township (since renamed to Green Brook Township) on April 2, 1872.