C&O Canal Lock 22
The Potomac River has a lot of natural obstacles that get in the way of water transportation. The lock was first built in 1822 by the Chesapeake and Ohio Canal. Also called the Pennyfield Lock, the simple design was actually quite difficult to carry out. Once it was put into place it allowed merchants to transport coal, grain, and other products to Washington and Georgetown. The nearby Lockhouse is apparently open for accommodations. To visit the lock there is an entrance fee of $10.