Not to be confused with Penn's Neck Township, a municipality in Salem County which no longer exists.Penns Neck is an unincorporated community located within West Windsor Township in Mercer County, New Jersey, United States. The community developed at the intersection of the Trenton-New Brunswick Turnpike and Washington Road. The Penns Neck Circle and the historic Penns Neck Baptist Church are both located in Penns Neck.