At Point of Rocks (MP 42.8), where the speed limit is 30 mph, the Old Main Line diverges to the east-northeast and the main line turns southeast, with the brick depot in the apex between the diverging lines. There's a single-track east leg of the wye, passing east of the depot, with a dirt road grade crossing on it. The speed limit rises to 65-55 as soon as the junction is cleared, with long stretches of 70 mph for passenger trains along the way, and the line passes a bridge over a road below, Intermediate Signals at Tuscarora, a dirt track grade crossing, a bridge over a side river, Intermediate Signals (new signals in service, in 2007) at Pepco (MP 37.0), where it leaves the river behind, a road bridge overhead, a bridge over a road below, a road alongside to the northeast, a bridge over a stream, Dickerson (MP 35.5), a crossover constructed in 2012, Intermediate Signals at MP 33.5, the MARC passenger station at Barnesville (MP 33.4), with its parking lot on the northeast side, a bridge over a road below, a road bridge overhead, an embankment in the woods, and then a cutting, extra track on the north side, and a bridge over a road.
There are B&O-style signals and crossovers at Buck Lodge (MP 30.0), on a short jog to the south, a bridge over a road below, B&O-style Intermediate Signals at Boyd (MP 28.9), a wide road bridge overhead (I-270), the MARC passenger station with platforms on both sides at Germantown (MP 26.4), a crossover constructed in 2012, two road bridges overhead, a bridge over a stream, Waring, detectors and B&O-style Intermediate Signals at Clopper (MP 24.3), a road bridge overhead, a grade crossing, a bridge over a road, a bridge over a divided limited-access highway (a spur from I-270), Brown, gated extra track on the north side, a grade crossing, a road bridge overhead, the MARC passenger station at Gaithersburg (MP 21.6), a footbridge overhead at the station, a grade crossing, a railroad museum on the north side just east of the grade crossing, a grade crossing, a road bridge overhead, a grade crossing, and dual road bridges overhead (another spur from I-270).
There is a road bridge overhead, the MARC passenger station (two side platforms) at Washington Grove, where the line turns south, a grade crossing, a bridge over a road, a bridge over Interstate 270, a spur on the north side trailing in, a grade crossing, a road bridge overhead, a grade crossing, east-facing spurs on the north side, old silos on the north side, a road bridge overhead, a road alongside to the north, a grade crossing, dual road bridges overhead, a road bridge overhead, a gated spur to industry on the north side, crossovers at Derwood (MP 19.6), a road bridge overhead, MP 19, dual road bridges overhead (the beltway? I-70?), a spur to a packaging plant on the north side, MP 18, a spur track on the north side curving northeast into a gated industry, a footbridge overhead, a bridge over a street, and new Intermediate Signals (MP 16.77), replacing those at Randolph Road, brought into service in 2008, at the west end of the passenger station (two side platforms with arched sheds) at Rockville (MP 16.7), where the line turns south-southeast and enters the DC suburbs with the Washington metro Red Line alongside to the southwest.
The line continues past the replaced Intermediate Signals at Randolph Road (MP 16.65/.66/67), a road alongside to the north, a road bridge overhead, a bridge over a divided road, Audrey Park, a road bridge overhead, Malpine, a grade crossing, the MARC passenger station at Garrett Park (MP 12.4), a grade crossing, Intermediate Signals (MP 11.8), a road bridge overhead, detectors at MP 11.6, Intermediate Signals at Kensington (MP 11.24/11.2-1), the MARC passenger station (short platform on the north side) at Kensington (MP 11.0), where the line turns east-southeast, a street alongside to the north, Intermediate Signals (MP 10.66), a road bridge overhead, the MARC passenger station at Forest Glen, where the line turns south-southeast again, a street alongside to the north, embankment, a grade crossing, a bridge over a divided highway, three road bridges overhead, and a road bridge overhead at crossovers at Georgetown Junction (MP 8.3), where a line to Georgetown (on the river) once headed west and the speed limit falls to 60-30,
There is a MARC passenger station at Silver Spring (MP 7.5), where there is a road bridge overhead and the other end of the Metro Red Line passes beneath the north track and rises up in between the two ex-B&O tracks to its own platforms, a bridge over a street, a road bridge overhead, a private road bridge overhead, a bridge over a street, Takoma Park (MP 6.3), as the line enters the District of Columbia, where there is a Red Line station on its tracks in the center, a bridge over a road, a wide road bridge overhead, a bridge over a road, a Red Line station at Fort Totten with the Green Line passing below, Intermediate Signals at Lamond, a street alongside to the northeast, a Red Line station at Brook Lane, Chillum, and a road bridge overhead.
The Red Line drops down in the middle, passes beneath the track on the north side, and rises on the north side of the double track, past Intermediate Signals at Terra Cotta, where the line turns south, a road bridge overhead, the Red Line Rhode Island Avenue station on the north side of the line, a bridge over a north-south street, University, a double-track Red Line bridge overhead, and the crossovers at QN Tower (MP2.1), where the north leg of a wye turns east to F and the speed limit falls to 30 mph. There are storage tracks for MARC trains in the 'vee' of the wye, a road bridge overhead, a bridge over a street, the New York Avenue Red Line station on the west side, and the main line reaches the Northeast Corridor at New York Avenue Tower, where there is a bridge over the eponymous street, just to the north of a bridge over a street at the end of the platforms in Washington Union Station (MP 0.0), which has a road bridge overhead midway along the platforms.
Many of the former B&O Position Light signals along this line have been replaced since 2004 (such as those at Rockville), with Safetran signals replacing those at, for example, QN Tower in March, 2012.