Milltown is a borough in Middlesex County, New Jersey, United States. As of the 2010 United States Census, the borough's population was 6,893, reflecting a decrease of 107 from the 7,000 counted in the 2000 Census, which had in turn increased by 32 from the 6,968 counted in the 1990 Census.Milltown was incorporated as a borough by an act of the New Jersey Legislature on January 29, 1889, from portions of North Brunswick Township, based on the results of a referendum held three days earlier. The borough was reincorporated by resolution of the borough council on May 2, 1896. A portion of East Brunswick Township was annexed in 1902. Originally known as Bergen's Mill, named for Jacob I. Bergen who owned the grist mill, the name is believed to have become "Milltown" from residents "going to the mill in town".As of the 2000 Census, the center of population for New Jersey was located in Milltown, at Milltown Road, just east of the New Jersey Turnpike.