Chesapeake and Ohio Canal National Historical Park | LOCK 5 AND DAM 1 GUARD LOCK

Upstream end of Lock 5

Upstream end of Lock 5


Lock 5 and the Dam 1 Guard Lock are located at Mile 5 on the C&O Canal towpath. There is a dirt parking lot at the site. See the Locks and Lockhouses web page for an interactive location map.


Lock 5 is a very popular spot on the Chesapeake and Ohio Canal. When I stopped by, many cars were outfitted with kayak and bike racks. I don’t believe there is any easy access to the Potomac River, but you can launch your boat into the canal itself and paddle quite a ways downstream before hitting Lock 4 in Georgetown, which is the end of the line for downstream paddling trips. There were also a lot of hikers and bikers starting their journeys on the towpath from here.

Lock 5 is the center of activity for bikers, hikers, and kayakers

Lock 5 is the center of activity for bikers, hikers, and kayakers

Along with a standard canal lift lock is the Dam 1 Guard Lock. A guard lock connects the canal to its source of water—in this case the Potomac River. The gates on the lock can be opened and closed to regulate the amount of water that flows into the canal. When you have a long canal such as the C&O (184 miles), you need to establish water sources every so many miles. The water that enters through this guard lock provides water for the five-mile segment from here down to the start of the canal in Georgetown.

But what happens during times of drought when there is hardly any water in the Potomac River? That’s where dams come in. Dams were built at various locations on the river so that deep pools of water were available during times of low rainfall. There were seven dams on the Chesapeake and Ohio Canal, including Dam 1 just .75 mile upriver. The water is diverted at the dam into a long and narrow natural channel that runs between the mainland and High Island until it flows into the Dam 1 Guard Lock.

Dam 1 supplied water for the shortest section of canal of any of the seven dams. The reason for this was because back when the Chesapeake and Ohio Canal was in operation there were so many water-powered mills in this area that siphoned off the water that there was only enough water left for the five-mile stretch between here and Georgetown.

It’s hard to picture this network of water control devices simply by standing at Lock 5, but if you take a look at the satellite image below from Google you can clearly see the layout.

Layout of Lock 5 and guard lock

Layout of Lock 5 and guard lock

Upstream view of the Lock 5 gates

Upstream view of the Lock 5 gates

To keep the waters of the Potomac River from flooding into the canal, the National Park Service usually plugs guard locks with stone or concrete. However, here at the Dam 1 Guard Lock this was not done, so the lock still works. Why? Well, from here on down to Georgetown the canal is kept watered so canoeists and kayakers can paddle on the canal.

Water flowing through the Dam 1 Guard Lock

Water flowing through the Dam 1 Guard Lock

The small strip of land between Lock 5 and guard lock has been covered in concrete to protect the two structures during times of flooding.

View looking across the concrete cover from Lock 5 to the guard lock

View looking across the concrete cover from Lock 5 to the guard lock

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Last updated on April 23, 2020
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