There are several historic canal sites in the northern half of the national park including Frazee House, Alexander Mill and Lock 37, Lock 39 Tinker Creek Aqueduct and the Visitors'Center. .Go to the park homepage and click on "Towpath Trail sites to visit" for information on all the points of interest or click on "Towpath Virtual Tour".
Alexander's Mill and Lock 37 are about three miles from the northern end of the national park. In this area the canal looks much better, but the towpath is not as shady and it is close to a fairly heavily traveled road.