A bit of history from the nps.gov website: There are over 1,300 historical structures along the C&O Canal. Lockhouses, aqueducts, dams and pumphouses are just a few of the engineering marvels of the 19th Century found on the canal. The canal was literally a man-made river. To make the canal work a complex system of hydrology was constructed. To supply water for the canal seven feeder dams were built on the Potomac River from Cumberland to Little Falls. To control the water, seventy-four lift locks were placed in the canal. Each lock raised or lowered a boat approximately eight feet. The locks allowed boats to travel upstream or downstream and made it possible to overcome the elevation difference of 605 feet between Georgetown and Cumberland.
