East Millstone is an unincorporated community and census designated place (CDP) located in Franklin Township, in Somerset County, New Jersey, United States. As of the 2010 United States Census, the CDP's population was 579. It is a small rural community that grew and prospered with a small industrial base in the 19th Century, centered on the Delaware and Raritan Canal at Amwell Road and the long-abandoned Millstone and New Brunswick Railroad that terminated in East Millstone.