The Millstone River is a tributary of the Raritan River in central New Jersey in the United States. The Millstone River begins in western Monmouth County and flows westward through northern Mercer County and northward through southern Somerset County, draining into the Raritan River at Manville. Almost three quarters of its length is paralleled by the Delaware and Raritan Canal. Both the Millstone River and parallel canal provide drinking water to large portions of central New Jersey and provide recreational uses as well. Course The Millstone River starts in western Monmouth County at , near CR-524 (Stage Coach Road). It flows northeast and turns north before picking up a tributary and crossing CR-1, Sweetmans Lane. It then crosses Baird Road before crossing SR-33 and flowing past the watershed of the Cranbury Brook. It turns west, crossing Perrineville Road and Applegarth Road. Meanwhile, it receives many small tributaries. It crosses the New Jersey Turnpike, before flowing through the East Windsor Open Space Acquisition. It then crosses CR-639 and Route 130 before picking up a tributary and flowing into Fischer Acres Associates. It crosses Old Cranbury Road and turns southwest before receiving Rocky Brook and making a turn to the northwest. It then turns west and crosses Old Trenton Road, John White Road, and Southfield Road before flowing alongside the West Windsor Planning Incentive and crossing Cranbury Road. It receives Cranbury Brook and Bear Brook before receiving Devils Brook and crossing US-1 (Brunswick Pike). It then flows into Carnegie Lake and crosses the D&R Canal, which it closely parallels the rest of its downstream journey. It turns northeast, receiving Stony Brook from the southwest before turning north again. It receives Harrys Brook and exits the Carnegie Lake. It then enters the D&R Canal State Park before crossing NJ27. It receives Beden Brook before crossing the Griggstown Causeway and receiving the Simonson Brook directly afterward. By the time it receives Beden Brook, it is paralleled by CR-533, River Road. It then receives the Ten Mile Run and Six Mile Run before crossing Blackwells Mills Road. It receives a tributary from Colonial Park and crosses Weston Causeway. It receives Royce Brook before flowing past the Somerset Christian College, one of the few structures built on the land between the D&R Canal and the Millstone River. By the time it crosses Royce Brook, CR-533 has separated from it and turned into Manville. It joins the