Keywords: Lock 20 Chesapeake and Ohio Canal drawing from HABS.png en Drawing of Lock 20 Great Falls Tavern showing butterfly valves and conduits to fill lock 1828 design style lock HABS says HABS MD 16-____ 19B- sheet 1 of 1 - Chesapeake Ohio Canal Lock No 20 MacArthur Boulevard Great Falls Montgomery County MD http //www loc gov/pictures/collection/hh/item/md0875 sheet 00001a/ LOC-image hhh md57 Historic American Buildings Survey MD-57-E 39 00222 -77 24639000000001 Chesapeake Ohio Canal National Historical Park Locks water transport |