Blackwells Mills is situated on the West Bank of the Millstone River about two miles south of Millstone. A mill was first built there in 1746 by Peter Schenk. Through his daughter, the mill passed to the Mercer family, and later sold to Blackwell, who built a house on the land. The mill burned and was rebuilt in 1885 and further restored in 1943. The canal along the river from Millstone to Blackwells Mills was once a major force in the commercial development of the entire State of New Jersey. It was built to complete connections in a series of inland waterways from New York to Florida.
Perhaps the single most important boost to the identity of the Township as we now know it occurred on May 31, 1771. On that date, Hillsborough was officially granted a Charter incorporating it as a Township. The records of Hillsborough Township are complete from their inception in 1746 and there are ten volume, each some several hundred pages, kept in the Special Collections Department of Rutgers University Library along with the Charter.
Hillsborough Township quickly took its place in history as the path General Washington and his troops traveled from the Battle of Princeton to winter quarters in Morristown. While the British were encamped in the valley below awaiting an opportunity to attack, it is said that Washington drilled his troops on the Sourland Mountain around a spring near the top using different formations and corn stalks for guns. As the sun caught the stalks, the British thought Washington had received reinforcements and fresh supplies and the British troops, thinking that they were outnumbered, slipped off to New Brunswick leaving Washington to continue to Morristown.