Hidden in the woods along Walnut Creek, near Millport, stands this forgotten and rarely seen guard lock. The canal boats would pass through Lock # 31, cross Walnut Creek through a slack water, and then pass through this guard lock.

In 1833, William Foresman built a gristmill on his property along Walnut Creek. The Foresman Mill, a.k.a. the Good Intent Mill, quickly became a landmark in Harrison Township. In 1879, Edward K. Campbell acquired enough money working on the Cromley Farm to purchase the mill. Campbell converted the mill from water power to steam power and installed a roller system. Campbell's Mill had a daily capacity of 50 barrels. The goods were shipped to other areas on the canal boats. Campbell was one of the most successful and well known millers in the township. He was also a highly respected man and a model citizen.