Downstream view of Lock 45 on the Chesapeake and Ohio Canal just as it merges with the Potomac River

Lock 45 is located at Mile 107 on the Chesapeake and Ohio Canal towpath. It is .2 mile downstream from Lock 46, which has vehicle parking. See the Locks and Lockhouses web page for an interactive location map.

Dam 5, which is located just a half mile downstream from Lock 45 on the Chesapeake and Ohio Canal, caused the waters of the Potomac to pool behind it, essentially forming a small lake. This served two purposes. First off, the deep pool was used to supply the canal with water even in times of drought. The water was diverted into the canal, passing through the guard lock that could be opened and shut to regulate the water flow.

Second, the upstream water level was now constantly high enough for boats to travel directly on the river between the dam and Lock 45. This is called slackwater, and it saved the C&O Canal Company the expense of having to dig a canal. Boats traveling upstream would pass through the Dam 5 guard lock and enter the Potomac River, then continue on the river until reaching Lock 45, where they reentered the canal. Of course boats traveling downstream exited the canal at Lock 45 and reentered at the dam.

The Potomac River was actually at a lower elevation than the canal, so in addition to serving as an entry and exit point between the canal and river, Lock 45 was a lift lock. However, none of the wooden gates or hardware survive today.

While it would appear to be a money saving decision, there was a technical reason for the canal bypass as well. Between Lock 45 and Dam 5 is a cliff, and it would have been impossible to blast a canal into the rocks. In fact, the towpath between the two is a concrete path that hugs the rock walls. Mules still pulled the boats while on the river, thus the need for a towpath.