Along the six miles of the C&O Canal that run past Potomac, the four car entrances people know best are Carderock, Great Falls, Swains Lock and Pennyfield. This fall only one of them works the way it normally does. In its October 14 update, the National Park Service listed the Great Falls Tavern area with its lot, restrooms, overlook and trails all open. The other three each had a construction note attached.
If you usually drive past the busy main lot to a quieter trailhead, that habit needs adjusting this year. The usual alternates are the ones under repair. And in December the one entrance that is fully working cuts back its own days.
Carderock Is Open, With Less of Everything
Carderock, at mile 10.5, never closed. The Park Service lists the Carderock Pavilion and the parking lots as open. There's a catch, though. A tunnel repair has kept an alternating one-lane closure in place at the Carderock tunnel since July 27, 2026. Parking Lot 1 is open with reduced capacity because the contractor stages equipment there.
The restrooms are also closed for emergency repairs, and portable toilets stand in for them. The tunnel work is part of a larger NPS project covering the Carderock, Four Locks and McCoys Ferry tunnels. That project page says the towpath and recreation area stay open while the work goes on. It doesn't give a finish date.
Carderock still works for a quick towpath walk. It's a weaker choice for a long morning with kids, guests or a dog that needs a big lot.
Swains Lock Is Paying Off a 2019 Storm
Two miles upstream from Great Falls, the Swains Lock parking area at mile 16.7 closed on October 13. The cause goes back seven years. On July 8, 2019, a flash flood eroded the embankments along the Great Falls entrance road on MacArthur Boulevard and damaged the timber retaining wall around the Swains lot. According to the NPS repair page, crews are taking out that wall and replacing it with an embankment of fill and seeded topsoil. The money comes from the federal Emergency Relief for Federally Owned Roads program.
The two official sources give different reopening timelines. The Park Service says the closure "will continue for several weeks." The C&O Canal Trust runs the overnight rental at Lockhouse 21. Its Lockhouse 21 page estimates the work will finish around the end of October and says some reservation dates were blocked. For a reader on October 29, that means the lot could reopen any day now or stay closed into November. The Canal Quarters at Lockhouse 21 stay accessible the whole time, and the Swains hiker-biker campground is still listed as open.
While the lot is closed, the Park Service points towpath users to the closest lots on either side, which are Great Falls at mile 14.3 and Pennyfield Lock at mile 19.6.
The Upstream Alternate Has Its Own Crews
Pennyfield has work of its own. DC Water is repairing a critical section of the Potomac Interceptor sewer line near Lock 22, and the Park Service warns of possible delays on Pennyfield Lock Road. The MoCo Show reported in June that the emergency work near Pennyfield was planned to run from June 15 through September, with crews and heavy equipment possibly visible to park users. September has come and gone. DC Water's project page still describes work at Pennyfield as continuing and doesn't give an end date.
The same sewer line is the reason for a caution notice downstream at Lock 10, near Cabin John. DC Water is managing an overflow there, and the Park Service says visitors may notice odors. Bethesda Magazine covered the original January collapse and reported at the time that the towpath had not been breached and stayed open. According to DC Water, the second phase of environmental restoration around the collapse site is expected this fall, including repairs to the canal liner and replanting.
Where the Stretch Stands, Entrance by Entrance
Here is the October 14 picture side by side. The Park Service updates its current conditions page as things change, so check it before you load the car.
| Access point | Mile | Parking | Restrooms | Current note |
|---|---|---|---|---|
| Carderock | 10.5 | Open, Lot 1 reduced | Closed, portable toilets | One-lane tunnel closure since 7/27/26 |
| Great Falls Tavern | 14.3 | Open | Open | Entrance road open, possible single-lane flagging |
| Swains Lock | 16.7 | Closed since Oct. 13 | Lockhouse water stays on | Reopening estimated late October to "several weeks" |
| Pennyfield Lock | 19.6 | Not listed | Not listed | DC Water work, possible road delays |
Great Falls has a caveat too. The entrance road is open, but the 2019 flood repairs there run through 2026, weather permitting. Crews close one lane at a time now and then, so delays coming and going are possible. A larger repaving project is still being designed and has no construction date. The Park Service says more than 1 million people visit Great Falls, Maryland, every year.
What Great Falls Still Offers Right Now
Past the entrance road, nearly everything at Great Falls is listed as open. That includes the Great Falls Tavern Visitor Center, the Great Falls Overlook and Olmsted Island Boardwalk, the Gold Mine Loop, the River Trail, and Sections A, B and C of the Billy Goat Trail. Within the Gold Mine Tract, the area between MacArthur Boulevard and Berma Road, visitors have to stay on designated trails.
Section A of the Billy Goat Trail is the piece most likely to close without warning. The Park Service usually closes it when the river gauge at Little Falls reaches 5 feet and reopens it once the gauge falls back to 4.8 feet. During business hours, the Tavern visitor center at 301-739-4200 has the latest.
The canal looks different too. Great Falls boat rides have ended for the season. Every fall the Park Service drains the watered sections to protect the stone masonry from freezing, the same practice the C&O Canal Company followed when the canal was operating. As of October 14, Widewater and the reach from Lock 17 to Lock 21 still held water, and Locks 21 through 23 were already dry. Water usually comes back in early spring. Walking upstream from the Tavern past Swains now means walking beside an empty canal bed.
There's also a water note for anyone heading out longer. Around mid-November, the park shuts off faucets at camping areas so the pipes don't freeze. The restrooms at Great Falls Tavern draw municipal water, and the park's list shows their tap as potable.
December Shrinks the Anchor
Starting December 1, Great Falls Tavern Visitor Center goes to its winter schedule, which runs through February 28: open 9 a.m. to 4 p.m. Thursday through Sunday, closed Monday through Wednesday. It also closes on Thanksgiving, November 26, and on December 24 and 25. Christmas Eve falls on a Thursday and Christmas on a Friday this year. Put that together with the winter schedule and the visitor center is open only Saturday, December 26, and Sunday, December 27, that week. That's the week a lot of households have guests in town who want to see the falls.
The center's hours page hasn't been updated since early June, so confirm the dates against the Tavern page closer to your visit.
Building a Canal Outing Around the Closures
With the alternate trailheads limited, the rest of an outing matters more. These are the dated stops still ahead this season:
- Wednesday through Sunday. Old Angler's Inn on MacArthur Boulevard lists hours Wednesday through Sunday and takes reservations. Its site says beer-garden hours and live music depend on the weather.
- November 4. The last 2026 date for the Norman's Farm CSA and pop-up market at Cabin John Village, which started its run on April 29.
- December 5 and 6, 11 a.m. to 5 p.m. The Cabin John Village Holiday Market on the Community Green at 11325 Seven Locks Road. It's the first weekend of the Tavern's winter hours, so a morning at the falls and an afternoon at the market both fit on Saturday or Sunday.
- December 9, 5 to 6:30 p.m. Chabad Potomac's Glow in the Dark Chanukah Spectacular on the same Community Green.
Our team at Pearlman Meekin & Co. keeps track of the details that shape everyday life in Potomac, from which trailhead lot is open to how close a street sits to the towpath. If you're thinking about a home near the canal side of Potomac and want to talk through what that access looks like through the seasons, book a consultation with us.
