East Millstone is an unincorporated community and census-designated place located in Franklin Township in Somerset County, in the U.S. state of New Jersey. As of the 2010 U.S. 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.