The Georgetown Branch
The branch left the CSX (ex-Baltimore & Ohio) main at Georgetown Junction, near Silver Spring, MD. Some maps show a short segment of branch in operation near the main line; it might have lasted a few years there as there are warehouses and light industry near the old main line connection.
An auto club map shows the line extending all the way to the Maryland-D.C. border; this might have been for service to "Filter Plant Siding" indicated on the SPV atlas. In the atlas, the line is shown going from Georgetown Junction in Maryland to Chevy Chase, Bethesda, Dalecarlia Reservoir, into D.C. to "Filter Plant Siding", and into Georgetown.
The furthest end of the line paralleled the Chesapeake & Ohio canal into Georgetown. The years of construction and abandonment are not known, but the line was in service as recently as 1981, as it was used when the Smithsonian ran the "150th year anniversary" of the John Bull locomotive, the oldest operating steam locomotive still in existence.
The northern section of the line is now a paved trail called the "Georgetown Branch Trail". Further south, in the Bethesda area, the paved trail is known as the "Capital Crescent Trail". The line passes through deep cuts and has not been built on, but it is in a heavily built up area so there is a lot of car traffic.
The rails are still in place at the location of the Connecticut Ave (MD Route 185) crossing, as this street is probably too congested to close off for rail removal.
I distinctly remember switching equipment positioning rolling stock on this line near the River Road crossing (also near the Roy Rogers) in the late 1980s.
Went to high school in Washington 1968-71, and the Georgetown Branch had daily service at the time. CSX put welded rail down on the line in 1980, and I believe it was abandoned in the late 1980s. A stub may have remained in service for a few years, as you note.
At least until 1981, the line went all the way to Georgetown. There was a small yard off K Street on what is now the site of the Sequoia restaurant and the Scandinavian Cultural Center, adjacent to the mouth of Rock Creek.
I lived in Bethesda, MD until 1969. The abandoned siding shown in the River Rd. crossing photo serviced the warehouse that was a part of the Marriott Corp., main office. The B&O RR made a drop there each weekday until Mariott moved their office. The section of Georgetown Branch between the East-West Hghwy overpass and Columbia CC passed behind the houses accross the street from my home.
My friends and I used to cross the railroad trestle on Brookeville Road, near radio station WWDC, to visit a friend who lived off Jones Bridge Road. Clearly, we were young, fearless and stupid. Never dodged a train, but heard one in the distance once.
During 1978-79, I worked in one of the office buildings at Arlington, and got to observe the operations across the river at Georgetown. Service at that time was usually three days a week MWF with a crew out of Eckington Yard. On several occasions I had an opportunity to walk across the Key Bridge and observe more closely. The crew told me that on Tuesdays and Thursdays, they usually made a trip on the branch that went through the Anacostia area of Washington DC, past Andrews AFB, and terminated south of the base. At this time, there were still two customers left at the very end of the Georgetown Branch, at the foot of 30th St, right where Rock Creek flowed into the Potomac. There was a small power plant that provided steam to some of the government buildings nearby, as I recall it had two tracks that each held four hopper cars. The other customer was a building supply receiver that got boxcars and flatcars of lumber. The B&O once had a freight station in this area, but I believe it was torn down when the Whitehurst Freeway was built over K Street in 1948-49.
The usual operation was that the train from Eckington Yard would pull into the siding along the boathouse area west of the Key Bridge, then the engine would cut off, run around the train, and shove into the street trackage on K Street, all the way to the end. Even back then, the area was very congested, and the train would tie up traffic on K Street, sometimes for up to two hours while they did their switching. On one occasion that I saw, DC police were called to arrange for towing of a parked vehicle that obstructed the track near the Key Bridge. Once the switching was done, the crew would pull their train back to the siding west of the Key Bridge. Sometimes the crew would switch the train to get the caboose on the rear for the return to Eckington Yard. On other occasions, they just continued with the caboose right behind the locomotive. The typical power was a lone GP9. Only once did I see a train with two units, both GP9's.
Today, the Swedish Embassy occupies the area where I saw GP9's placing boxcars and flatcars of lumber. Another office building just to the north of the embassy occupies the area where the steam plant once stood.
Line went out of service in 1985. GSA steam plant switched to trucks from a Transload in Bladensburg MD until it switched fuel sources. T.W. Perry in Chevy Chase was the last customer - it switched to transload from Earl Bell in Silver Spring until going entirely to truck.
In earlier times (1950's) there was a switcher stationed in Georgetown and a road freight from Eckington that would make several trips up and down the branch (the Georgetown switcher made it as far as Georgetown Junction) and would exchange cars in Bethesda, Georgetown or Georgetown Junction. The two freights would both switch customers. Lumber yards at Chevy Chase, Bethesda and Georgetown; Concrete plants in Bethesda and Georgetown; Betco Block off River Road (Bethesda); Marriott and filtration plant as noted; Wilkins Rogers Flour in Georgetown; coal to Georgetown (several customers) and Bethesda.