Lock 12 is one of the most well-preserved locks of the old Susquehanna and Tidewater Canal. It paralleled the Susquehanna River for 43 miles between Wrightsville and Havre de Grace, Maryland. It was built between 1836 and 1839 and opened in 1840 for commerce between the greater Harrisburg area and the Chesapeake Bay. The canal carried lumber, coal, iron, and grain bound for Baltimore, Philadelphia, and New York until it was abandoned in 1895.
Lock 12 is 17 feet wide, 170 feet long, and had a lift capability of 8.8 feet. It was one of 28 lift locks built to overcome a 233-foot elevation difference between terminal points. While the Conestoga Navigation Company, a slackwater canal between Lancaster and Safe Harbor, was in operation it was said a person could board a ship in Lancaster, PA and depart in Paris, France. Although there’s no evidence that anyone actually ever did that.