Skillman is an unincorporated community and census-designated place located within Montgomery Township, in Somerset County, in the U.S. state of New Jersey. As of the 2010 United States Census, the CDP's population was 242.The area is served as United States Postal Service ZIP Code 08558. However, the Skillman postal address covers an area significantly larger than the Skillman CDP. The Skillman postal address services approximately half of the 32 square miles and approximately 23,000 residents comprising Montgomery Township.