Mile 84.6 down to Harpers Ferry
The C&O Canal towpath is the Maryland angler's road along this river, and its mileposts are the easiest way to talk about where you are. Dam 4 sits at canal mile 84.6 near Downsville, with its portage on the Maryland side; above it are the power company dam at Williamsport at mile 99.4 and the high Dam 5 at 106.6. Below Dam 4 the river runs through long ledges and grass beds toward Shepherdstown and Dam 3, which the Park Service marks at mile 62.3, and from there down to the US 340 bridge below Sandy Hook at mile 59.5 it is whitewater, class II and III around Harpers Ferry.
That stretch between Dam 4 and Dam 3 is the classic wade-and-canoe smallmouth water: broad, shallow in late summer, and cut with ledges that hold fish along their downstream edges. The Park Service maintains boat ramps along the canal and reminds boaters that Maryland rules govern the river itself and that life jackets are required in whitewater sections.
Brunswick, Point of Rocks and the Monocacy
Below Harpers Ferry the river widens past Brunswick and Point of Rocks, both with bridges and canal access, and the gauge this page reads sits at Point of Rocks with 9,651 square miles of watershed above it. Maryland DNR's September 16, 2026 fishing report called flows on the upper river steady, said cool nights were starting to drop water temperatures, and rated smallmouth fishing good on tubes, swimbaits, paddletails and small crankbaits.
Downstream of the Monocacy's mouth the rules change: from the Monocacy down to Dam 2 at Seneca Breaks, canal mile 22.1, the Potomac is a catch-and-release bass area all year. You may not possess a largemouth or smallmouth there at any time.
March 1 to June 15 and the other bass rules
Everywhere else on the nontidal river, Maryland's general bass rules apply: 12-inch minimum, five a day and ten in possession, with harvest open from June 16 through the last day of February. Between March 1 and June 15 you can fish, but every bass goes back, which covers the spawn. Walleye carry a 15-inch minimum year round and, from January 1 to April 15, a 20-inch maximum on the mainstem from about half a mile above Chain Bridge up to the spillway in Cumberland; the daily limit is five. Striped bass and hybrids caught in nontidal rivers cannot be kept.
A nontidal license for a Maryland resident rose to $32 for 2026; nonresidents pay $55, or $45 for seven days. The Park Service asks anyone who lands a northern snakehead to report it, with a photo if possible, to fishingreports@dnr.state.md.us.
Seneca to Chain Bridge: the fall line
Below Seneca the river heads for the fall line, and the character changes from wading water to a gorge. The Park Service lists canal miles 14.5 down to 4.2, Great Falls to Chain Bridge, as class IV and V whitewater where many people have drowned, and it posts the warning as bluntly as that. Fish it from the rocks at Great Falls or the shore below Little Falls if you know the footing, and do not wade or float it on a guess.
Below Chain Bridge the river turns tidal, and the tidal Potomac, with its striped bass and blue catfish, runs on a separate set of rules outside this page.
Point of Rocks: using the record
No outfitter publishes a wading range for this gauge, so the 2,000 to 6,000 cfs band here is taken from the USGS record at Point of Rocks. Summer and early fall monthly means sit near 4,460 cfs in July, 4,180 in August, 4,230 in September and 4,970 in October, against 19,000 in March and 16,150 in April. Around those late-summer numbers the Dam 4 to Brunswick ledges are wadeable and a canoe drags only on the shallowest riffles; as the gauge climbs past 6,000 the river colors and the ledges go under. In the three weeks before September 24, 2026 the gauge ran 1,510 to 2,570 cfs, at the very bottom of that band, which means clear water, fish tucked against grass and ledges, and long walks between good spots.
The bass year on the upper river
Smallmouth are on the rocks and feeding hard before the spawn in April and May, all released until June 15. Summer is a crayfish and minnow river, with topwater early and late, and in August the evening white fly hatch brings bass up for spent-wing patterns. September and October are the fall feed as water drops through the 70s, and by November the fish slide into deeper pools where streamers fished slowly take the bigger bass.