Locks 62, 63 1/3, 64 2/3, and 66
Mile 154.2 - Lock 62
Mile 154.5 - Lock 63 1/3
Mile 154.6 - Lock 64 2/3
Mile 154.7 - Lock 66
That rather ugly concrete lockhouse belongs to Lock 62. Lock 65 was never built and the fractional numbering of the locks is supposed to compensate for it by incrementing the lock spacing by 1 1/3 instead of 1. These four locks are all within a mile and very similar to the previous wood or concrete lined locks.
It's at this point the canal leaves the side of the Potomac for an overland shortcut (see the map on the UP button). This series of locks leads to the Paw Paw Tunnel which forms the greater part of the shortcut.
Between locks 62 and 63 1/3 is a small pond and waste weir.
Look closely at the walls of lock 64 2/3 and you can see the iron pegs that were used for affixing the lumber to the walls of the lock.
Even some of the bypass flumes were made of concrete.