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. East Millstone was an independent municipality from 1873–1949.