Penwell is an unincorporated community located within Lebanon Township in Hunterdon County, New Jersey, United States. Penwell is a community in the north of Lebanon Township that was also most northern settlement in Hunterdon County. It was known as Penwell dating back to 1866 and was named after the Penn Well Mills on the Musconetcong River. When the property of Sylvanus Hoffman was advertised for sale in 1886, the village was described as being on the Washington Turnpike (now Route 57) and his land "along a stream".