Millstone, then called Somerset Courthouse, was the county seat of Somerset County from 1738 until the British burned it to the ground in 1779 during the American Revolutionary War. After the victory at Princeton on January 3, 1777, General George Washington headquartered at the , while the army camped nearby that night. The next day, they marched to Pluckemin on the way to their winter encampment at Morristown.